































































































































































































































































































































O* g°* c 4, ^ * « - J * * *4 

*<* °-> -C *** <,° * 


<* c« MC V ' 


* * K 






EVERYDAY ELECTRICITY 










45,000-Kilowatt Curtis Steam Turbine and Generator at the Detroit 

Edison Company’s Plant. 


Courtesy of the General Electric Company. 

Synchronous Converters at the Plant of the Anaconda Copper Mining 
Company, Great Falls, Montana. 

GENERATORS AND CONVERTERS 


















THE USEFUL KNOWLEDGE BOOKS 

Edited by GEORGE S. BRYAN 


EVERYDAY 

ELECTRICITY 

A SIMPLE INTRODUCTION TO COMMON 
ELECTRIC PHENOMENA 

BY 

HERBERT T. WADE 

EDITOR FOR APPLIED SCIENCE AND TECHNOLOGY, “THE NEW INTERNATIONAL 
ENCYCLOPAEDIA ” AND “THE NEW INTERNATIONAL YEAR BOOK”; AUTHOR 
OF “SCALES AND WEIGHING — THEIR INDUSTRIAL APPLICATIONS”, 

AND (WITH WILLIAM IIALLOOK) OF “THE EVOLUTION OF 
WEIGHT8 AND MEASURES AND THE METRIC SYSTEM ”j 
ONE-TIME CAPTAIN, ORDNANCE DEPARTMENT, 

U. 6. A., IN CHARGE OF SPECIAL REPORT 
BRANCH, INFORMATION SECTION 


With Many Full-page Illustrations and Numerous 
Diagrams in the Text 


N ON-REFER ? 





BOSTON 

LITTLE, BROWN, AND COMPANY 

1924 













Copyright , 1924, 

By Herbert T. Wade. 

All rights reserved 

Published July, 1924 






Printed in the United States of America 



JUL - B '2A 


©C1A80010G 



EDITORIAL INTRODUCTION 


Need exists for writing of a new sort. Research 
in the physical sciences has been rapidly adding 
to the stock of data; and, with the development 
of new ideas, older ideas have been extended, 
modified, or discarded. Applied science has been 
changing the world in which we live. And not 
only science in these stricter fields, but also sci¬ 
ence in that broad sense of systematized knowl¬ 
edge, has been accumulating through experiment 
and experience a fund of special information. 

In such matters as these, nonprofessional read¬ 
ers in increasing numbers are seeking enlighten¬ 
ment. They are not, of course, likely to seek 
it from professional treatises or highly technical 
texts. At the same time, they have come to 
know how unsatisfactory “popularized” compila¬ 
tions so often are. They wish knowledge or¬ 
ganized to meet their particular requirements, 
and adequately rendered into simpler, humanized 
terms. 

For such readers The Useful Knowledge Books 
are intended. The volumes are by writers care¬ 
fully selected, both for authority and for ability 


VI 


EDITORIAL INTRODUCTION 


to treat their respective subjects with breadth, 
tact, and an individual touch. They are com¬ 
pact but properly comprehensive. Each is based 
on a fundamental plan, not merely assembled. 
All have certain features of arrangement and 
contents designed to make them as helpful as 
possible. The purpose is to have them at once 
reliable and readable. The illustrations are abun¬ 
dant, appropriate, and complementary to the text. 

This volume, “Everyday Electricity ”, is by 
Herbert T. Wade, who, as research worker, a 
former member of the teaching staff at Columbia 
University, editor of reference works, contributor 
to technological journals, and author, is particu¬ 
larly well equipped for the task. He explains 
the principles and phenomena of electrical action, 
and then makes clear how electricity is adapted 
to those more or less familiar uses in which in¬ 
telligent lay folk are interested. His volume is in 
greater part based on recent first-hand investiga¬ 
tion, and brings between its covers a wide range 
of information. In this “electric age” it should 
have wide appeal. 


G. S. B. 


FOREWORD 


In our everyday life, contact with electrical 
phenomena is made at so many points that ori¬ 
gins and fundamental relations are too often ig¬ 
nored. For many of these, the explanations are 
far from simple, and there are involved abstruse 
science and complicated engineering; but it is 
very desirable at least to make an attempt to 
understand the phenomena of our daily expe¬ 
rience with electricity. To do this, we conven¬ 
iently can start with a few fundamental ideas 
and definitions and then seek to develop the 
subject; although it must be realized that it is 
indeed a large subject, and even a modest plan 
is an ambitious task for a simple work like the 
present one to essay. We shall seek, however, 
to give the reader an idea of what electricity is 
in the light of modern science, and explain some 
of its more familiar aspects and phenomena when 
these are susceptible of popular exposition; men¬ 
tioning also others where the process is too com¬ 
plex and where we must be satisfied with the de¬ 
scription of the results rather than with their 
explanation. Be that as it may, if we can at least 


FOREWORD 


viii 

appreciate the electric light on the wall, the purring 
of the motor, the telephone on the desk, the click 
of the telegraph in the railway station, the trolley 
car passing our door, or other of the everyday 
applications of this mysterious force, we have 
accomplished something; and if this little book 
aids in that direction, it will have accomplished 
its object. 

Finally, it may be said that the author is under 
obligations to the General Electric Company, the 
American Telephone and Telegraph Company, 
the Westinghouse Electric and Manufacturing 
Company and the Western Union Telegraph 
Company for illustrations that aid materially 
in the presentation of the subject. Most of all 
he is indebted to his friend, Professor F. W. 
Hehre, of the Department of Electrical Engineer¬ 
ing of Columbia University, who had the kindness 
to read the proof and to furnish many valuable 
suggestions that have been thoroughly appre¬ 
ciated. 


Herbert T. Wade 


CONTENTS 


Editorial Introduction. 

• 

PAGE 

V 

Foreword. 


vii 

List of 

Illustrations. 


xi 

CHAPTER 




I 

Electricity — Its Fundamental Nature 


3 

II 

Static Electricity — Electricity at Rest 

22 

III 

The Magnet and Magnetism 


30 

IV 

The Generation of Current — The Vol- 



taic Cell ••<••• 


36 

V 

Electrical Units and Measurements 


48 

VI 

Induced Currents .... 


62 

VII 

Storage Batteries .... 


70 

VIII 

Generators and Motors 


76 

IX 

Direct and Alternating Current 


96 

X 

The Telegraph. 


101 

XI 

The Telephone. 


126 

XII 

Electric Lighting .... 


154 

xm 

Applications of Electrical Energy 


176 

XIV 

The Transmission and Distribution of 



Electricity. 


187 

XV 

Electricity and Transportation 


193 



X 


CONTENTS 


CHAPTER 

XVI 

Electricity on Shipboard 

• • • • 

PAGE 

210 

XVII 

Electric Heating 

• • • • 

213 

XVIII 

Electrochemistry and the 

Electric Fur- 



nace .... 

• • • • 

218 

XIX 

Electric Waves . 

• • • • 

233 

XX 

X-Rays .... 

• • • • 

241 

XXI 

Lightning 

• • • • 

250 

Glossary. 

• • • • 

259 

Bibliography .... 

• • • • 

279 

Index 



287 







ILLUSTRATIONS 


Generators and Converters . . . Frontispiece 

PACINO PAGE 

Benjamin Franklin.8 

From an Engraving by J. A. O’Neill 

Electric Motors.84 

General Electric Company’s Type of Street-Rail¬ 
way Motor. — Westinghouse Squirrel-Cage Induc¬ 
tion Motor 

Transformers .98 

Steel-Clad Transformer to Reduce the Voltage of 
a Transmission Line to That Required for the Light¬ 
ing and Power Circuits of the Consumer. — Large- 
Capacity Oil-Cooled Transformer, as Employed on 
Long-Distance Transmission Lines 

The Telegraph.106 

An Ordinary Telegraph Key and the Vibroplex. — 
Operator Sending a Message with the Vibroplex. — 

Front View of Switchboard in the New York Office 
of the Western Union Telegraph Company 

The Telegraph.114 

Receiving Operators at the Western Union Tele¬ 
graph Company’s Main Office in New York City. — 
Sending and Receiving Apparatus of the Multiplex 
System, as Used by the Western Union Telegraph 
Company 



ILLUSTRATIONS 


Xll 


Manually Operated Switchboard at a Large 

Central Station. 

Operator and Portion of “A” Board. — Operator 
and Portion of “B” Board 

Modern Telephone Equipment .... 
American Telephone and Telegraph Company’s 
Standard Dial Instrument. — Vacuum-Bulb Re¬ 
peater in Its Socket. — General View of a Machine- 
Switching Installation 

Electric Locomotives. 

Westinghouse Single-Phase Locomotive. — Gen¬ 
eral Electric Company’s High-Speed Gearless Passen¬ 
ger Locomotive 

Vacuum Tubes. 

1,000-Kilowatt Vacuum Tube in the Research Lab¬ 
oratory of the General Electric Company at Sche¬ 
nectady, N. Y. — Coolidge Radiator X-Ray Tube 


PAGE) 

138 


142 


206 


244 



EVERYDAY ELECTRICITY 



EVERYDAY ELECTRICITY 


CHAPTER I 

Electricity — Its Fundamental Nature 

In our everyday life, we are surrounded by ap¬ 
plications of electricity in various forms; so many 
and so simple, in fact, that we are likely to take 
them for granted as necessary to our comfort and 
convenience, or almost to our very existence. On 
land, at sea, in the air, wherever we may be, 
we employ numerous simple electrical devices 
that contribute to the ease of our daily living. 
Simple, yes; nothing could be more simple than 
turning the switch of our electric light, whether 
it be in the heart of a great city, on the farm, or 
in the portable hospital on the very battle front. 
Simple, yes, to apply to our own ear the radio¬ 
telephone and hear the news of the day. Simple, 
indeed, to board the railway train that a monster 
machine, without smoke or steam, draws along¬ 
side of our station platform, or that carries us over 
the mountains almost noiselessly. Simple to 


4 


EVERYDAY ELECTRICITY 


pick up the telephone and in a few minutes in¬ 
dulge in clear conversation with a distant person, 
with distance offering no bar. 

But when we think of the simple things (and 
we should think of the simple things about us), 
are they really so simple after all? And is not 
their complexity one reason why we do not think 
of them ? Thus we have a paradox, namely, that 
simple things are complex; but if we put our 
minds to it, we find after all that complex things 
are really simple. In other words, in electricity, 
as elsewhere, complex things and phenomena are 
really made up of simple elements; and if we can 
understand these elements, then we can under¬ 
stand the result attained, even if at first it some¬ 
times seems to us incomprehensible. 

We hear of “ wizards ” in electricity who bring 
to us wonderful inventions, but rarely do we hear 
of the ceaseless and methodical labors of these 
and other workers in the electrical field. Industry, 
quite as much as inspiration, has been the guid¬ 
ing star of these men; for in electricity there have 
been few happy and chance hits, or what we may 
call bursts of genius. Genius there has been 
and is in plenty; but genius self-controlled or 
directed by a master mind in a logical and orderly 
way. 

In connection with electricity, the first salient 
fact that strikes us is that here we are overcoming 
distance. Naturally, we make comparisons. The 


FUNDAMENTAL NATURE 


5 


old-fashioned pull-bell in its action was limited 
by the distance over which its wires could be 
stretched. The steam engine or the gasoline 
motor must generate its power “ on the job ”, 
that is, near to where it is utilized. The flag or 
the semaphore signal is limited by the range of 
visibility; the oil lamp or the gas burner, by the 
proximity of the reservoir of fuel. With elec¬ 
tricity, the energy generated or transformed can 
be sent over a considerable distance, whether it is 
to the incandescent lamp of the farm independent- 
generator set, or by the hydroelectric transmis¬ 
sion line from a mountain stream that by means 
of a dam has been converted into a storage res¬ 
ervoir. We have had to transport great turbines 
over rough roads that involve a transportation 
feat of no mean order. Or we place them at the 
foot of some cataract, such as Niagara, and build 
canals, tunnels, or pipe lines to bring the water 
under head to these great machines that are 
whirling the mighty generators. 

Now, given a source of electric current, we can 
see how the current is transmitted at high tension 
over long distances, as from Pitt River to San 
Francisco, in California, or from Niagara Falls to 
Lockport, in New York. Then, how is it utilized ? 
Always there are the needs for power to operate 
our electric railways, to light our buildings, to 
drive our machinery. The electricity is “ stepped 
down”, as the electrical engineers say, to a lower 


6 


EVERYDAY ELECTRICITY 


tension, and used as we need it. It will be 
apparent that what has been secured is concen¬ 
tration in generation at a point of maximum 
cheapness of production; economy and ease of 
transmission over long distances; and finally, flexi¬ 
bility of utilization, with the obvious economy to 
the consumer. If this can be done where there is 
water power, why not also generate electricity at 
or near the coal mines, and transmit current over 
conductors instead of carrying the fuel in coal 
cars, to be burned at the local boiler ? 

The Early Aspects of Electricity. The science 
of electricity is really modern, yet among the un¬ 
explained physical phenomena recorded by the 
ancients as early as Theophrastus (c. 372-287 
b.c.) and handed down through the ages, was the 
peculiar property of amber, when rubbed, to draw 
to itself light objects. This was observed by the 
Greeks, perhaps by that early scientist and philoso¬ 
pher, Thales of Miletus (c. 640-c. 546 b.c.) ; but 
beyond being recorded, it aroused no special con¬ 
cern until a.d. 1600, when William Gilbert of Col¬ 
chester (1544-1603), Queen Elizabeth’s surgeon 
and one of the great scientists of his day, found 
that a glass rod and a score of other materials, 
when rubbed with silk, also possessed this prop¬ 
erty. Seeking to designate this phenomenon, he 
went back to the Greek; and taking the name 
for amber, r/Xeurpov , states quaintly in his classic 
work on the magnet, “De Magnete”, published 


FUNDAMENTAL NATURE 


7 


in 1600, that it pleased him to call the force thus 
manifested “ electricity ”, saying that his glass 
rod had become electrified or amberized (or, in 
modern parlance, had acquired a charge of elec¬ 
tricity) . 

In 1738, Charles du Fay (1699-1739), a French 
physicist, found that sealing wax, too, if he rubbed 
it with cat’s fur, could be electrified. Here, how¬ 
ever, the phenomenon differed from that of the 
glass; for electrified sealing wax would attract 
an electrified substance that the glass repelled, 
while in turn it repelled such electrified bodies as 
the glass attracted; and du Fay straightway 
made the distinction between “ vitreous ” and 
“ resinous ” electricity. 

Benjamin Franklin’s Theory. Hardly more 
than this was included in the sum total of knowl¬ 
edge in this field in 1747 when the American states¬ 
man Benjamin Franklin (1706-1790) turned his 
attention in this direction. In 1747, he intro¬ 
duced the terms “positive” and “negative”, ar¬ 
bitrarily to distinguish the two kinds of electrifi¬ 
cation. A body repelled by a glass rod rubbed 
with silk he termed positively electrified; a body 
repelled by sealing wax rubbed with cat’s fur he 
called negatively electrified. These terms science 
adopted and has since retained. 

Franklin, however, went farther and sought to 
explain the nature of the phenomenon; and as¬ 
serting that positive and negative electrical charges 


8 


EVERYDAY ELECTRICITY 


always are found simultaneously and in exactly 
equal amounts, advanced the theory that elec¬ 
tricity must exist “ in normal amounts as a con¬ 
stituent of all matter in the neutral or unelectri¬ 
fied state.” If there were more electricity than 
normal, then there would be a positive charge; 
whereas if the supply were less than normal, then 
there would be a negative charge. 

The Nature of Electricity. Now, this theory 
was more than an interesting speculation by a 
scientific genius; for it involved a deep insight 
into the nature of the problem and suggested a 
solution that, more than a century and a half 
later, scientists were only too glad to consider. 
Other physicists at about Franklin’s time, or a 
little later, put forward the two-fluid theory, which 
dominated electrical science for over a hundred 
years. In this, the assumption was made that 
matter which contains as essential constituents 
equal amounts of the two fluids without weight, 
termed, respectively, positive and negative elec¬ 
tricity, would be in a neutral or normal condition; 
whereas if it contained a preponderance of one 
or the other, there would be the appropriate 
charge. 

But Benjamin Franklin assumed that there must 
be an electrical particle or atom, and such a view 
seemed to him, as it did to some later scientists, 
fully to explain the electrical phenomena of the 
day. A century later, in 1871, Wilhelm Weber 


















FUNDAMENTAL NATURE 


9 


(1804-1891) established his theory of electro¬ 
magnetism on practically the same basis and was 
able to explain various additional phenomena 
that science had developed. The great German 
scientist Hermann von Helmholtz (1821-1894) said 
that as a logical consequence of the acceptance of 
the hypothesis that the elementary substances are 
composed of atoms, “ we cannot avoid conclud¬ 
ing that electricity also, positive as well as nega¬ 
tive, is divided into definite elementary portions 
which behave like atoms of electric!ty.” 

Through the efforts of Hendrik Lorentz and 
others in the early years of the twentieth century, 
these theories of the material nature of electricity 
in the form of a minute particle or atom be¬ 
came generalized; so that a logical result was the 
modern electron theory, in support of which we 
now have experimental proof of the nature of the 
electron. 

The Electron. In fact, it is one of the triumphs 
of modern science (and by that is meant the science 
of the present century) that it now affords us some 
definite idea of the structure of matter and the 
nature of electricity. Ever since the days of the 
Greek philosophers Leucippus (c. 600 b.c.) and 
Democritus (c. 460-c. 357 b.c.) and later of the 
Roman Lucretius (c. 96-55 b.c.), men have in¬ 
dulged in the theory that matter was made up of 
atoms; and in later and modern times, a theory 
that it was composed of molecules and atoms 


10 


EVERYDAY ELECTRICITY 


served the chemist or physicist who was not too 
inquisitive as to their general nature. The mole¬ 
cule, which was made up of atoms, was, it will be 
recalled, the smallest portion of matter that could 
exist and maintain its essential characteristics; 
and the atom was the smallest conceivable amount 
of an element, and united with other atoms to 
form molecules. But to-day we find not only 
that there is a close connection between matter 
and electricity, both possessing an atomic nature; 
but that electricity is a component of all atoms 
of matter, for there is that minute particle known 
as the negative electron, which has been shown to 
exist as an individual entity of small mass. 

Each atom, we are told, has a somewhat com¬ 
plicated structure; in fact, is an electrical system, 
as well as what once we might have called a ma¬ 
terial system. It has a certain number of elec¬ 
trons, which we find are but negative electricity; 
and it also has a certain number of protons, or 
particles of positive electricity, even smaller than 
the electrons. Normally, each atom would be 
composed of a requisite number of electrons and 
protons; but it is found that the electrons may be 
added to or subtracted from the atom and thus 
give rise to the condition known as a charge of 
electricity; or, when we consider the actual mo¬ 
tion of these electrons, to what is termed a current. 

Therefore, it must be realized that everything 
— every substance — contains electricity; that 


FUNDAMENTAL NATURE 


11 


electricity is a fundamental component of matter; 
but that the presence of this electricity is indicated 
only when the electricity is found to a greater or 
less amount than usual in an object, or when it 
is in motion. When sealing wax is rubbed with 
cat’s fur, for example, we have what is familiarly 
known as a negative charge, and modern theory 
indicates to us that the sealing wax has too many 
electrons; whereas the different phenomenon, as 
when glass is rubbed with silk, receiving what is 
known as a positive charge, would indicate that 
there were too few. In other words, the electrons, 
or particles of negative electricity, are movable and 
can be added to, or removed from, the atom. On 
the other hand, the positive charge that enters into 
the composition of the atom and that normally 
would neutralize the negative, is a perpetual 
feature of the atomic structure. As we under¬ 
stand it now, the electrons move freely; but the 
proton, or positive-charge element, is indis¬ 
solubly connected with the atomic structure. 
Thus it is possible, by the addition or subtrac¬ 
tion of electrons, to secure at the atom a pre¬ 
ponderance of either negative or positive charges. 
Of course, electrons are all the same as regards 
nature and size; but the attraction that one special 
atom has for an electron varies in the case of dif¬ 
ferent kinds of atoms. 

In the case of metals, it would seem that this 
attraction is comparatively weak; with the re- 


12 


EVERYDAY ELECTRICITY 


suit that the electrons are much more free to move 
from place to place, so the metal becomes what 
is termed a conductor. With the nonmetals, on 
the other hand, there seems to be a relatively 
greater attraction exerted on the electrons, and 
their movement from place to place is resisted; 
or in other words, the material is a nonconductor. 
Bearing this condition in mind, it is not hard for 
us to realize that what we call an electric current 
passing through a body must be in reality a stream 
of electrons whose motion the nature of the body 
permits. In this motion it is now known that the 
actual flow is from what long has been known con¬ 
ventionally as the minus terminal to the con¬ 
ventional positive terminal, or opposite to the 
conventional direction of the current. 

Electricity Not “Produced.” Since it is clear, 
then, that an electric current, or electricity in 
its movable state, consists of electrons in motion, 
it will be understood that electricity is not “ pro¬ 
duced ”, nor can any machine or device be de¬ 
veloped to produce electricity. What really hap¬ 
pens is that electricity is moved or driven; and 
this moving or driving involves the expenditure 
of mechanical or chemical energy. Thus, in a 
battery, the chemical action between the solution 
and the elements forces out the electrons at the 
negative pole and causes them to flow around the 
wire circuit, and through the positive terminal 
again to enter the battery. 


FUNDAMENTAL NATURE 


13 


It is not electricity that our meter shows we have 
consumed in our lighting circuits, but electrical 
energy; for just as many electrons leave any part 
of the circuit as enter it, whether the case be that 
of a lamp, a motor, or an electric heater. The 
passage of the stream of electrons acts to set the 
atoms in a more violent vibration, and this is 
evidenced in the case of the lamp by the incan¬ 
descence of the filament; and in the case of the 
heater by the glowing wire. 

Effects of the Current. The nature of the elec¬ 
tric current has been suggested in the movement 
of the electrons, but it is rather by its effects that 
it is readily and generally recognized. The effects 
produced are familiar in our ordinary experience, 
and we can study them with far easier understand¬ 
ing than we can the ultimate nature of electricity. 
Thus, we know that an electric current will cause 
magnetism, and will produce chemical action. By 
its passage through a conductor it will produce heat; 
and by its magnetic effects it can be made to do 
work, as in the case of the ordinary electric motor. 

Important Discoveries in Electricity. Such, in 
brief outline, are the fundamental conceptions 
of electricity as they have been developed by 
brilliant men of science in the nineteenth and 
twentieth centuries. Abstract theory always was 
accompanied by experiment and research, so that 
the discovery of new phenomena has been followed 
by their application to useful purposes. 


14 


EVERYDAY ELECTRICITY 


When Alessandro Volta (1745-1827) discovered 
in 1794 the cell that bears his name, he made 
available for many purposes a constant flow of 
electricity. With this voltaic current, Sir Hum¬ 
phry Davy (1778-1829) was able to make a number 
of important and original experiments and dis¬ 
coveries, among which were the production of the 
electric arc in 1800, through which he laid the 
foundation of future illumination by electricity; 
and the decomposition of salt solutions, so as to 
obtain as elements the metals sodium and potas¬ 
sium. Another step of almost equal importance 
in this direction was taken when in 1800 Sir 
Anthony Carlisle (1768-1840) and William Nichol¬ 
son (1753-1815) decomposed water into its con¬ 
stituent elements, hydrogen and oxygen, by the 
use of the electric current. 

Then came the notable discovery by H. C. 
Oersted (1777-1851) of Copenhagen, in 1820, that 
in the space around the conductor carrying an 
electric current there is developed a condition 
termed a magnetic field, because it exerts an in¬ 
fluence on a magnetic needle placed there. Oer¬ 
sted found that when a compass needle free to 
move was placed near a conductor carrying a 
current, the needle was deflected so as to set it¬ 
self at right angles to the wire; and that when the 
needle was above the wire its north pole would 
point in one direction, while if it were below it 
would point in the opposite direction. Oersted 


FUNDAMENTAL NATURE 


15 


very properly reasoned that this was due to a 
magnetic field of force being produced by the 
current around the conductor, and that the direc¬ 
tion of this magnetic field of force lay in circles 
whose planes were perpendicular to the wire. 

The Early Electromagnet. After this, there was 
an important development when William Sturgeon 
(1783-1850), in 1825, invented the electromagnet 
with a single winding of rather thick copper wire. 
This Joseph Henry (1797-1878), in 1828, straight¬ 
way improved upon by winding around his iron 
core not one layer but many turns of fine silk-in¬ 
sulated copper wire, and secured electromagnets 
of much greater capacity. Not only did Henry 
produce an electromagnet capable of lifting sub¬ 
stantial weights, but he also showed that it could 
be operated from a distance, and that one electro¬ 
magnet could be used to open and close another 
magnetic circuit, ring a bell, or perform other use¬ 
ful work; thus clearly suggesting the transmis¬ 
sion of signals and power. 

The Discovery of Induction. Henry also dis¬ 
covered the action of one circuit upon another, or 
mutual induction. Then came Michael Faraday 
(1791-1867), the brilliant British experimentalist, 
who discovered in 1831, among various allied 
phenomena, the fundamental one of an induced 
electric current being generated in a conductor 
forming part of a closed circuit and moved 
across the lines of magnetic force in the mag- 


16 


EVERYDAY ELECTRICITY 


netic field existing about the poles of a mag¬ 
net. This discovery, realized experimentally, in¬ 
spired inventors to develop machines by which 
a current was so produced; and in 1831 H. Pixii 
brought out apparatus in which a permanent 
magnet was rotated in front of coils, or spools, 
of wire, and an alternating current generated. 
This magneto-machine was the germ of the mod¬ 
ern alternating-current generators. Later, Pixii 
also fitted one of his machines with a crude com¬ 
mutator, so as to produce direct current. 

Practical Applications of Electricity. These and 
other discoveries were of extraordinary signifi¬ 
cance and of vast scientific bearing; but as yet, 
electricity met with little practical use outside, 
let us say, of Franklin’s lightning rod. In 1837, 
however, S. F. B. Morse (1791-1872) developed 
the idea of the electric telegraph; and this by 
1844 was realized in practical form, so as to trans¬ 
mit messages between Washington and Baltimore. 
An extension of this idea was the submarine cable, 
which in 1858 was laid between Great Britain 
and America, to serve for only a couple of months 
by reason of the impairment of the gutta-percha 
insulation through the high-potential currents 
used; but which later, in 1865, was made com¬ 
mercially efficient and serviceable. 

Development of the Generator. Returning for 
the moment to the experiments of Faraday and 
the crude magneto-machine of Pixii, it is inter- 


FUNDAMENTAL NATURE 


17 


esting to record that the improvement and de¬ 
velopment of this machine appealed to many 
inventors. Joseph Saxton (1799-1873), in 1833, 
and E. M. Clarke, in 1835, devised magneto¬ 
machines (with commutators) in which coils of 
wire, termed the armatures, were rotated in front 
of the magnet, giving direct current; and by 1849 
a magneto-machine giving alternating current 
was built of sufficient size to supply current for 
an arc lamp in the lighthouse at South Foreland, 
England. 

Improvements on these electrical machines 
followed rapidly; first, in the form of the shuttle- 
wound armature, which Werner von Siemens 
(1816-1892) invented in 1856, with the arrange¬ 
ment of pole pieces so curved as to inclose the 
armature — for by this time electromagnets had 
replaced the permanent magnets, thus furnishing 
greater intensity of magnetic field. Then came 
the armature that employed an iron ring on which 
to wind the coils, an improvement independently 
invented by Antonio Pacinotti in 1860, and by 
Z. T. Gramme in 1870. In the meantime, how¬ 
ever, it had been discovered that by passing all 
or part of the current developed at the armature 
through the electromagnets, the machine would 
be self-exciting. 

From Gramme’s invention of the ring armature 
in 1870, the beginning of electrical engineering 
may be said to date; for previously, the practical 


18 


EVERYDAY ELECTRICITY 


/ 

applications of electricity had been almost ex¬ 
clusively to land and submarine telegraphy, with 
some attention to electroplating. Now electric¬ 
ity had passed to a practical stage, and apparatus 
and machines were brought out from the labora¬ 
tories to be placed at the service of mankind. The 
first notable effort was in electric lighting, which 
originally through the efforts of Charles F. Brush 
and others became established as an industry in 
the United States. 

In 1878 came Thomas A. Edison’s invention 
of the incandescent electric light and lighting sys¬ 
tem. This was nothing less than epoch-making, 
for one man by his own efforts made possible 
a complete and important industry; not only 
providing a lamp and generator of special design, 
but developing a central source of power, with a 
distribution system and all, even to the keys to 
turn the current to the lamps. 

An equally important industry had its birth 
in 1876, when Alexander Graham Bell invented 
the telephone; and this instrument soon developed 
by leaps and bounds as its utility became appre¬ 
ciated. Electric railways were the dream of many 
American inventors, even in the days when vol¬ 
taic batteries were the sole source of current. 
After many unsuccessful efforts, dating back to 
1835, when Thomas Davenport, a Vermont black¬ 
smith, developed a crude idea of a motor-driven 
car, the first practical success was realized in ex- 


FUNDAMENTAL NATURE 


19 


perimental lines built by Werner von Siemens 
and J. G. Halske in 1879 at Berlin, and by Edison 
in the following year at Menlo Park; though the 
first really extensive line to be operated for com¬ 
mercial service was that installed in 1887 by Frank 
J. Sprague at Richmond, Virginia. 

Large-sized generators were developed for elec¬ 
tric lighting with both direct and alternating 
current; and when the advantages of alternating 
current were realized, attempts were made for 
its wider utilization, especially for power. The 
invention and development of the transformer 
made it possible to distribute alternating current 
for lighting economically and at different voltages; 
and the invention of the synchronous motor, and 
most of all, that of the polyphase induction motor, 
made it possible to derive power in large amounts 
from alternating-current circuits. Accordingly, 
electrical energy could be generated cheaply and 
transmitted over considerable distances. 

The year 1895 was notable for the successful 
accomplishment of telegraphy through space by 
electromagnetic waves by Marconi, utilizing the 
discoveries of Hertz, Lodge, and others. This 
was the beginning of the great development in 
radio communication. 

The formulation by James Clerk Maxwell 
(1831-1879), in 1867, of the electromagnetic 
theory of light, in which he stated that light must 
be an electromagnetic phenomenon and that 


20 


EVERYDAY ELECTRICITY 


waves of light were electromagnetic waves, was 
a beginning for much valuable theorizing. Then, 
after the passage of electricity through gases had 
been studied by William (later Sir William) 
Crookes (1832-1919) and others, came the dis¬ 
covery of the X-rays by W. K. Roentgen, in 1895. 
Following this, was important work by J. J. Thom¬ 
son, dealing with the cathode rays — those rays 
sent out from the cathode (or negative pole) of an 
exhausted tube through which a current passes. 
Thomson found in 1896 that the X-rays caused a 
gas through which they passed to be a conductor 
of electricity, and then later demonstrated that 
the cathode rays consisted of minute masses, far 
smaller than the smallest chemical atom; having, 
in fact, only about 7^5 of the mass of an atom 
of hydrogen and a diameter only about io^ooo 
as great. Each one of these minute masses carried 
a negative electric charge. In his experiments 
carried on in 1898, Thomson was able to discover 
the electron; so that this theory is based upon 
sound experimental data. 

To-day there is every evidence of great activity 
in the study of electrical phenomena and theory, 
and electricity is being considered with a view 
to modern ideas of “ relativity.” Greater agen¬ 
cies than ever previously are at work in the labora¬ 
tory, and a wealth of discovery is promised. Just 
as the vacuum bulb of the laboratory of yesterday 
becomes the X-ray tube or the telephone repeater 




FUNDAMENTAL NATURE 


21 


of to-day, so there is a continued progress of dis¬ 
covery and application. Electricity has changed 
our modes of communication, illumination, power, 
and transportation, and has wrought changes 
second only to those made by steam. Some of 
these accomplishments it is proposed to discuss 
in the following pages. 


CHAPTER II 


Static Electricity. Electricity at Rest 

For many years, the phenomena attending the 
presence of charges of electrons on different 
bodies 1 seem to have had a rather less general 
interest, except for the scientist, than those in 
which the motion of electrons or charges was in¬ 
volved— in other words, electric currents such 
as were used for the telegraph and in electric 
lighting. It has already been noted that the 
Greeks, sometime about 600 b.c., knew that 
amber after friction with cloth would attract 
light substances; and that Gilbert of Colchester, 
Franklin, and others experimented in this field. 

The usual experiment is, first, to charge a glass 
rod by friction with silk, and then to present it to 
a pith ball suspended on a silk thread. The pith 
ball will be attracted until it touches the rod, when, 
having become electrified or charged, it will be 
repelled from the rod. Then it will be attracted 

1 We use the words “on different bodies”, for, generally speaking, 
it is only at the surface of a body that the charge resides. It is at the 
surface of separation between the body and some other body or sub¬ 
stance that there is an excess or deficit of electrons, determining 
the nature of the charge. Within the interior elements, are equal 
amounts of opposite kinds of electricity in a neutral state. 


STATIC ELECTRICITY 


23 



CD 


to the hand or any uncharged body; upon touch¬ 
ing which, it will become wholly or in part dis¬ 
charged or restored to its former neutral condition. 
Now, if two or 
more pith balls are 
charged from the 
glass rod in the 
given fashion, it 
will be found that 
they act to repel 
each other; as well 

as being repelled, of Fia 1 . (Left) Pith ball attracted by a p0Bi . 

Kir + V10 nrim’ tively electrified glass rod. (Right) Mutual 
LUUiac, Uy LUC Uilgl- repulsion of two positively charged pith balls. 

nal charging body. 

If we go through a similar chain of operations 
with a rod of vulcanite rubbed with fur, the charge 
of electricity thus produced is different from that 
produced by the glass rod; for the pith balls, 
attracted by the charged glass rod but repelled 
after being charged, are now attracted by the 
vulcanite stick that has been electrified. 

This difference in the nature of the charge can 
be determined by arranging various substances in 
a list on which a substance is positively electrified 
if rubbed or brought into contact with a substance 
lower on the list, whereas it becomes negatively 
charged if the contact is established with a sub¬ 
stance of higher position. Thus, our glass rod is 
positive when rubbed with silk, but it is negative 
if rubbed with fur or wool. 






24 


EVERYDAY ELECTRICITY 


The Gold-leaf Electroscope. The gold-leaf elec¬ 
troscope is also extensively employed in this con¬ 
nection, as well as with radium. A doubled strip 
of gold or aluminum leaf is suspended from a metal 
rod within a glass jar; or better, in a metal case 
provided with a glass window. If there is a 

charged body in contact with 
the upper extremity of this 
metal rod, the leaves will fly 
out from their vertical posi¬ 
tion, showing that they have 
been charged by conduction; 
the charge passing from the 
charged body along the 
metal rod. If the leaves 
were suspended from a rod of 
glass, let us say, there would 
be no deflection caused; 



Fig. 2: A Gold-leaf 
Electroscope. 


for, glass not being a conductor, the charge would 
not pass from the point of contact to the gold-leaf 
strips. 

The distribution of the charge will depend upon 
the proximity of other charges. For example, if 
we present to the gold-leaf electroscope a charged 
body, we shall find that the leaves are separated 
as they are when charged by conduction. We 
can also charge the electroscope by induction. 
That is, to give it a negative charge, we bring near 
it a glass rod that has been rubbed with silk. 
When the plate or knob of the electroscope is 



































STATIC ELECTRICITY 


25 


touched with the finger, the positive charge is 
repelled to the earth, leaving the negative charge 
held bound by the positively charged body brought 
near to the electroscope, so that when the finger 
is removed the charge on the electroscope is nega¬ 
tive. (This is, of course, conventionally speaking; 
actually, electrons pass from the earth.) If a 
piece of electrified sealing wax had been used, the 
electroscope would have received a positive charge 
under similar circumstances. 

The Electrophorus. In the electrophorus is a base 
of ebonite or shellac, on which may be placed a 





Fig. 3 : An Electrophorus. — (A) Base of ebonite or shellac, to which a 
negative charge is given with cat’s fur. ( 5 ) Metal plate placed on the 
base and negatively charged by conduction. (C) Metal plate connected 
to the earth by a finger: negative charge repelled and positive held bound. 
(D) Metal plate, positively charged, raised from the base. 

metal plate fitted with an insulating handle. To 
the ebonite a negative charge may be given by 
stroking it with cat’s fur, and then on it may be 













26 


EVERYDAY ELECTRICITY 


placed the metal plate, which will then, of course, 
receive a small negative charge, also by conduction. 
But by the touching of the metal plate with the fin¬ 
ger, to connect the plate with the earth, positive 
electricity will be attracted from the earth while 
the negative is repelled, and thus a positive charge 
will be given to the plate. (Again this is speaking 
conventionally; actually, electrons pass to the 
earth.) When the finger is removed, to break the 
connection with the earth, the positive charge is 
kept bound by the negative charge beneath. If 
we raise the plate and move it to a distance, we 
shall find, by testing it with an electroscope or 
otherwise, that it has a positive charge, and one, 
it may be, of relatively high potential; for if a 
connection is made to the earth, as by bringing 
the plate near to the hand, the high-potential 
charge of the plate will seek to get back to zero, 
and in this effort a bright, sharp spark may be 
produced. Then, of course, the cover or plate is 
uncharged; and the operation may be repeated 
as often as desired. Work is done in raising the 
positively charged plate or cover from the nega¬ 
tively charged base, and this acts to develop the 
high-potential energy of the plate. 

Electrical Machines. Naturally, since a glass 
rod can be charged by friction with silk, it would 
be very practical to have some mechanical way 
of doing this; and early experimenters employed 
a cylinder or plate so mounted as to be rotated 


STATIC ELECTRICITY 


27 


in contact with a silk surface. Then, by means 
of pointed conductors, the charge thus produced 
on the cylinder or disc was removed to charge 
some other substance or article, such as the Leyden 
jar of glass and tin foil, or some form of condenser. 
Machines for developing electricity by friction and 
then building up the charge by induction, were 
evolved; and influence-machines and other plate 
machines (as of Toepler, Holtz, and Wimshurst) 
were built with several discs, capable of producing 
sparks a number of inches in 
length. These devices could 
be used in medical work, for 
passing a spark through a 
vacuum tube, for igniting a 
combustible substance, or for 
other purposes. 

Condensers. The Leyden 
jar, invented as early as 1745, 
is of glass and coated within 
and without for about two 
thirds of its height with 
metal foil. Through the stopper closing the jar’s 
mouth passes a metal rod, terminating above in a 
knob and reaching down to the interior foil sur¬ 
face. By charging one coating of this jar with 
electricity, a difference of potential as regards the 
opposite coating is established, if that surface 
has connection with the earth; and such a charge 
can be built up of considerable amount. Two 



WMri 


Fig. 4: A Leyden Jar. 









































28 


EVERYDAY ELECTRICITY 


surfaces or plates oppositely charged would have 
little effect on each other if they were a distance 
apart; but let them be close together, and the 
positive charge on one becomes greater and the 
negative charge on the other less — that is, such 
an increased difference of potential has been pro¬ 
duced that a brisk spark may result on connec¬ 
tion or when the insulation breaks down. But 



Ground 


Fio. 5: The capacity of a negatively charged plate A is increased by bring¬ 
ing near it a second plate B, connected with the ground. Negative electricity 
is repelled from B and positive electricity brought to the plate, so that it be¬ 
comes charged positively. The potential of the negatively charged plate is 
lowered. 

the two plates must be separated by some insulat¬ 
ing material, and the two charged surfaces must 
be near together. In fact, the nearer the charged 
surfaces are, the greater will be their capacities. 
In the Franklin pane, the metal foil was attached to 
either side of a plate of glass; and naturally, when 
greater quantities of electricity were desired, the 
size and number of these plates could be increased. 

Any system of two conductors insulated from 
each other becomes a condenser. Sheets of metal 
foil separated by paraffined paper are a quite 






STATIC ELECTRICITY 


29 


usual form of condenser; and sometimes mica 
is also used as the dielectric, or insulator. The 
condenser is not merely an experimental device. 
It is frequently encountered in many kinds of 


+ 


+ 


Fig. 6: Arrangement of plates insulated from one another to form a con¬ 
denser. The capacity of the condenser depends upon the number and size 
of the plates, their proximity, and the nature of the nonconductor used as an 
insulator. A typical condenser can be made of sheets of tin foil separated by 
sheets of paraffined paper or mica, indicated by the white space in the diagram. 


electrical work: thus, a submarine cable or tele¬ 
phone wire, with respect to the earth, forms a 
condenser; a condenser at the subscriber’s in¬ 
strument is a feature of every telephone circuit; 
and condensers are employed in radio installa¬ 
tions. 

























CHAPTER III 


The Magnet and Magnetism 

The property of attracting small pieces of iron 
has long been known to be possessed by certain 
ore bodies, which first were found in Magnesia 
in Asia Minor, and gave rise to the name of mag¬ 
nets. Specimens of such ores may be studied as 
to this property by means of iron filings, as the 
old Roman philosopher Lucretius, who flourished 
in the first century before Christ, knew. The 
first obvious fact to be noticed is that there are 
always two or more spots where the iron filings 
tend to concentrate. These spots or small areas 
are termed the magnetic poles; and when a mag¬ 
net of two poles is suspended, free to move 
about a vertical axis, it will take a position where 
the line joining these two poles is in approximately 
a north-and-south direction. The two poles are 
referred to as the north-seeking and the south¬ 
seeking pole, respectively; or in short, the north 
and south poles. 

Stroking a bar of iron or steel with a natural 
magnet will produce an artificial magnet with 
similar properties as regards its power to attract 


THE MAGNET AND MAGNETISM SI 


iron and steel, and with two poles well defined, 
as may be determined by testing with the iron 
filings. But it is also found that all iron and 
steel does not become magnetized in the same 
way and to the same degree. A piece of soft iron 
soon loses its magnetism, particularly when the 
magnetized specimen is jarred, as by dropping or 
striking. On the other hand, if a piece of hard¬ 
ened steel is magnetized, it will retain its magnet¬ 
ism under many vicissitudes. 

This is a very important distinction, for on the 
respective magnetic properties of iron and steel 
depends much electrical apparatus. One machine, 
such as a transformer, requires a core of soft iron, 
which will magnetize readily but will give up its 
magnetism, once the magnetizing influence is re¬ 
moved ; whereas for 
the needle of a com- \ 

pass, or in the mag¬ 
net of a telephone, 
we need steel, which 
magnetizes to a high 
degree and will re¬ 
tain such magnet¬ 
ism. 

If a small bar of 
magnetized steel is 
suspended in a paper loop, or if a magnetized 
needle is stuck through a piece of cork and allowed 
to float in a liquid, then each will take up a 


•Suspend/ng j 
Thread 



Magnet 

Fig. 7: A Bar Magnet Freely Suspended. 
— Note that the same ends always point in 
the same direction and consequently are 
termed “north pole” and “south pole”, 
respectively. 







32 


EVERYDAY ELECTRICITY 


Magnet 


N 


Nj// 

2 


W 


Fig. 8 : The Magnetism of Iron. — The 
nail is magnetized by induction. 


north-and-south direction. Now, if such a steel 
magnet is broken, there will result two magnets, 
each with a north and south pole; and this proc¬ 
ess can be carried on indefinitely, indicating that 
the magnetism is a property not merely of the two 
poles but of the entire mass of the steel, and that 
the iron filings shown in Figure 9 are merely 
magnets. 

If we take a bar magnet and place near one 
end of it a nail (as indicated in the diagram), the 

nail straightway be¬ 
comes a magnet, as 
may be tested with 
the iron filings or 
the compass, and 
develops north and south poles. The nail has 
been magnetized by what we term induction, the 
magnetic influence of the permanent magnet 
having passed into the nail as it would into any 
magnetic material placed in the neighborhood. 

Two poles of the same kind always repel each 
other, and two unlike poles attract each other. 
The pole of one magnet that seeks the north will, 
when brought near a similar north pole, tend to 
move it away; if brought into proximity to a south 
pole, will attract it. 

If we take a bar magnet and study it by means 
of iron filings placed above it on a card or on a 
plate of glass, it will appear that the filings are 
concentrated in the neighborhood of the two 






THE MAGNET AND MAGNETISM 33 


poles; and furthermore, that these iron filings 
arrange themselves in definite and significant direc¬ 
tions. Here we have what is known as a magnetic 
field of force, or a region where magnetic force 
would be exerted upon a magnet pole. The mag¬ 
netic field is composed of magnetic lines of force; 



Fia. 9: The magnetic lines of force about a bar magnet, 
as indicated by iron filings. 


and the direction of these magnetic lines of force 
is the direction in which the north pole of the 
magnet is urged. And this is shown by the fact 
that each particular iron filing is really a small 
magnet, with its own north and south poles, and 
arranges itself in the direction of the lines of force. 

We shall see that there is also a similar magnetic 
field of force about a conductor carrying an elec¬ 
tric current. A moving electron is surrounded 
by a magnetic field; and as the result of an elec¬ 
tric current, magnetism is produced. This is 



34 


EVERYDAY ELECTRICITY 


demonstrated by the familiar experiment of plac¬ 
ing over a magnetic needle a conductor carry¬ 
ing a current. It will be found that the needle will 

Conductor Car/y/hj? Current 

4 - - ^ 



Fio. 10: Diagram to show movement of a magnetic needle under the in¬ 
fluence of a conductor carrying a current. The direction of deflection of the 
needle can be remembered by the device that the north pole of the needle will 
be deflected to the left hand of a man swimming in the current and facing the 
needle. If the conductor were below the needle, the deflection would be in the 
opposite direction. 

be deflected according to the direction of the 
current. 

The Electromagnet. Whenever we wish a 
strong magnet, much stronger than a natural 
magnet, or than one we can obtain from rubbing, 
we use wire carrying a current of electricity and 
we wind it around an iron core; employing, of 
course, insulated wire, so that we can get as many 
separate turns of current as possible. The core 
then is magnetized by induction, as it is termed, 
just as was the nail; and naturally, the stronger 
the current and the greater the number of turns, 
the stronger will be the magnetic field and the 
magnetism developed. Whether the core is iron 
or steel, it will be strongly magnetized; if already 











THE MAGNET AND MAGNETISM 35 


a magnet, it will acquire a more powerful mag¬ 
netism ; and we have here an electromagnet, a 
device that underlies the telegraph, the generator, 
the motor, and much other electrical apparatus 
and machinery. 

In connection with the magnet, there is a mag¬ 
netic circuit in which the magnetic lines of force 
assume certain directions in going from the north 



Fia. 11: The Permeability of Iron. — Here the lines of force gather at the 
iron instead of passing around as they would were no iron present. 


to the south pole of the magnet. Now, these 
magnetic lines of force traverse different substances 
in different ways, and there are different conduc¬ 
tors for magnetism, just as there are for elec¬ 
tricity. The best of these conductors of magnet¬ 
ism is iron, and iron is said to possess “ perme¬ 
ability ” on account of the facility with which 
it carries the lines of force and permits of magnetic 
induction. No material has been found that will 
act as an insulation for a magnetic circuit. 













CHAPTER IV 


The Generation of Current. The Voltaic 

Cell 

Perhaps the simplest means with which we are 
familiar for developing an electric current is the 
voltaic cell; or, as we commonly term it, the elec¬ 
tric battery — though properly a battery is a 
group of two or more connected cells. Here, by 
chemical action, a difference of potential is main¬ 
tained between the two essential elements of the 
cell, consisting of pieces of metal in dilute acid, 
or of an equivalent arrangement. In terms of 
the electron theory, chemical action tends to force 
electrons to collect at one of the electrodes (as 
the pieces of metal are termed), and to remove 
them from the other. In other words, with a su¬ 
perabundance of electrons at one part of our cir¬ 
cuit and a deficiency at the other, if we establish 
connection by some form of conductor, an electric 
current results. 

For many years, the voltaic cell was practically 
the one source of electric current, but by its cost 
and the rapidity of its exhaustion it restricted the 
use and application of electricity. However, it 
was the basis of much of the early work, and Volta, 


THE GENERATION OF CURRENT 37 


when he arranged his so-called “ crown of cups ” 
(couronne des tasses), laid a foundation for the 
future work of many experimenters. As Sir 
Humphry Davy said in 1800, when this discovery 
was first announced to the Royal Society of Great 
Britain, “ the voltaic battery was an alarm bell to 
experimenters in every part of Europe.” 

What Volta did was to use a series of cups con¬ 
taining a dilute solution of acid or brine, and in 
these cups he placed strips of zinc and copper. 
Each zinc strip, where it emerged from the liquid, 
was attached to a copper strip that dipped into 
the solution in the next cup. 

At the extremities of the 
group of cups — namely, the 
copper strip at one end and 
the zinc strip at the other 
end — conductors could be 
attached, and from them a 
current of electricity be ob¬ 
tained. 

The Simple Primary Cell. 

Volta’s battery was, of 

course, the germ of the modern primary cell, 
which we may consider briefly. In its simplest 
form, there is a glass jar containing sulphuric 
acid diluted about twenty times its volume, or 
any other oxidizing acid. In this solution are 
inserted (as indicated in the diagram, Figure 12) 
a piece of copper and a piece of zinc, the upper 



Fig. 12: A Simple Voltaic Cell 
of Copper and Zinc in Dilute 
Acid. 







38 


EVERYDAY ELECTRICITY 


parts of which rise above the surface of the liquid. 
Although the acid first may attack the zinc plate, 
causing small bubbles of hydrogen gas to collect 
at its surface, there soon will be no evidence of 
chemical action so long as the two metals are not 
in contact. Once contact is made, there will be 
vigorous chemical action and hydrogen gas in 
bubbles will be liberated at the surface of the 
copper instead of at that of the zinc. 

The copper plate is always termed the cathode, 
and the zinc is the anode, these terms coming from 
the Greek, and indicating the element at which 
the current enters the liquid (in the case of the 
anode) and (in the case of the cathode) the ele¬ 
ment by which it leaves. Here, of course, as already 
suggested, use is made of that conventional mode 
of speaking of the direction of the current which, 
as we have seen, is really opposite to the actual 
motion of the electrons. It will be observed that 
it is the anode that dissolves away in the action 
of the solution, the metallic zinc being used as a 
source of energy. It is oxidized and consumed 
just as much as if it were being burned by heat, 
and the cost of the energy is the zinc and the acid 
that acts upon it, just as much as the cost of the 
energy of a steam engine is the fuel burnt to heat 
the boiler. 

The result of the chemical action is to give 
electrons to the zinc and to remove them from the 
copper, so that the zinc will have more than its 


THE GENERATION OF CURRENT 39 


usual quota and the copper less; a preponderance 
of electrons being produced at the negative termi¬ 
nal. If we connect the negative terminal with the 
positive by a wire, a steady stream of electrons 
will flow as the chemical action is maintained. 
This stream of electrons is the current, and the 
number of electrons in the stream determines the 
intensity of the current. 

Studying the arrangement of cells in the dia¬ 
gram and noting the conventional symbols, al¬ 
ways employed, of a short, thick line for the zinc 



and a long, thin line for the copper or carbon, we 
first see the cells in series (Figure 13). Here we 
shall find that the difference of potential or elec¬ 
tromotive force will be that of one cell multiplied 
by the number of cells; but inasmuch as we have 
the accumulated internal resistance (for the cur¬ 
rent has to flow through the solution in each of 














40 


EVERYDAY ELECTRICITY 


these cells), no more current will be developed 
than were we to employ a single cell. This of 
course is true only when there is no external re¬ 
sistance and the cells are short-circuited. With 
high external resistance, it would not follow. 

On the other hand, if our battery is so arranged 
that two or more copper or carbon elements are 



Fig. 14: A Voltaic Battery Connected in Parallel or Multiple. 


connected together, and two or more zinc ele¬ 
ments (as in Figure 14), we have what is known 
as a parallel or multiple arrangement; and al¬ 
though we have no greater electromotive force, 
we have cut down the resistance within the cells 
by affording an increased path for the current. 
In other words, the zinc plates would act together 
like a single zinc plate, and the copper or carbon 
plates connected together would act like a single 
copper or carbon plate. 















THE GENERATION OF CURRENT 41 


The Electrolyte. The solution in which the 
two elements of the battery are placed is known 
as an electrolyte, which is a chemical combination 
capable of dissolution into two or more ions. 
The molecules are broken apart, or split, into these 
ions, for this is the action that takes place within 
the battery. We distinguish between the elec¬ 
tropositive ions, such as zinc and hydrogen, which 
carry a positive charge from zinc to copper, and 
the electronegative ions, such as sulphion (S0 4 ) and 
chlorine, which are negatively charged and move 
in the opposite direction. There are, of course, 
various types of cells, with different elements and 
electrolytes, in which the chemical action is quite 
different; but the underlying basis is the same. 

Polarization. Whether we are using a cell in 
intermittent service — as for example, on a tele¬ 
graph line or bell circuit — or short-circuiting it 
to measure its current with a galvanometer, it 
will be apparent that it gradually grows weaker. 
At the copper plate of the simple cell there forms 
a film of hydrogen, which produces a counter¬ 
electromotive force. This cuts down the positive 
action of the copper, as well as increases the in¬ 
ternal resistance of the cell. This effect early was 
realized in the simple cell, and the chemist was 
called upon to find some means of replacing the 
hydrogen ions with others, such as those of cop¬ 
per or mercury, which did not act to produce polari¬ 
zation; or to surround the positive electrode — 


42 


EVERYDAY ELECTRICITY 


that is, the copper (or in later types of cells, the 
carbon) — with some chemical that would supply 
oxygen or chlorine to unite with the hydrogen 
before the hydrogen came in contact with the 
positive electrode. 

Internal Resistance. A cell may have a high 
electromotive force at its terminals but possess, 
through the electrolyte, such an internal resistance 
as to make it unavailable for many purposes. 
When the external resistance is large as compared 
with the internal, this is not such a serious matter; 
but when the line resistance is small and we de¬ 
sire a large current, this internal resistance be¬ 
comes an important item. 

Use of Batteries. A rough classification of vol¬ 
taic cells would be into (a) those designed for use 
on open circuits and ( b ) those for closed circuits. 
Familiar types of open-circuit battery are the 
Leclanche cell or a common dry cell, employed in 
such service as ringing an electric bell, or for the 
older types of telephone, or working the ignition 
system of a motor-car engine. On the other hand, 
for closed-circuit work, there would be used a sim¬ 
ple cell of copper and zinc, a Daniell or a gravity 
cell, or some of the many forms of carbon and 
zinc cells; for there have been developed numer¬ 
ous sorts, with various arrangements of porous 
cups and electrolytes. 

Daniell Cell. In the first attempt to prevent 
polarization in a voltaic battery, John F. Daniell 


THE GENERATION OF CURRENT 43 


Copper 

Sulphate 


(1790-1845) of London, in 1836, employed a po¬ 
rous jar of unglazed earthenware to contain the 
zinc rod or cylinder (which was the negative ele¬ 
ment of the cell) immersed in dilute sulphuric 
acid; the porous jar itself being placed in an ex¬ 
ternal glass jar containing a solution of copper 
sulphate, with a cylinder of sheet copper as the 
positive element. In this cell the polarization by 
hydrogen was entirely — 

avoided, because the hy¬ 
drogen acted to form zinc 
sulphate and water, which 
immediately dissolved the 
salt. For almost a cen¬ 
tury this cell proved to 
be one of the most useful 
types, and in some form 
or modification it was 
(and is) frequently seen 
in physical laboratories. 

Gravity Cell. This modification of the Daniell 
cell is most familiar, as it was once extensively 
used in telegraph offices, and still may be seen in 
isolated offices not employing storage batteries or 
generators. The blue solution of copper sulphate 
in the jars made these batteries easily recogniz¬ 
able, and the jars, row on row, were a conspicuous 
feature of many old-time telegraph offices or fire- 
alarm central stations. 

Here there is no porous jar, but the zinc, amalga- 



Fig. 15: A Gravity Cell. 




















44 


EVERYDAY ELECTRICITY 


mated and sometimes in the form of a so-called 
crow’s foot, is suspended in a weak solution of 
zinc sulphate, which, by its lighter specific gravity, 
rests on top of a solution of copper sulphate kept 
saturated by crystals of blue vitriol at the bottom 
of the jar. In this is placed a plate of sheet copper, 
folded in a sort of fan shape to secure increased 
surface. 

Leclanche Cell. Prior to the general use of the 
dry cell, the so-called Leclanche cell (devised in 
1868 by Georges Leclanche, a French physicist) 
was extensively employed to operate electric 
bells, electric signals, or telephones, and for other 
uses that required current intermittently for 
short periods but over a long time. This cell, 
under such conditions, furnished good service, 
and all the attention it required was replenishing 
with water, replacing of the sal ammoniac when 
exhausted, and renewing the zinc rod; but it was 
not capable of giving a steady, constant current 
for any considerable time because it polarized 
easily. It was, however, free from local action 
under most conditions. The Leclanche cell con¬ 
sists of a glass jar in which is placed a solution of 
sal ammoniac or ammonium chloride. The nega¬ 
tive element is a rolled zinc rod or pencil, and 
the positive electrode is a bar of carbon surrounded 
by a mixture of manganese dioxide and granulated 
carbon, tightly packed in a porous jar. On closed 
circuit, the zinc is acted upon by the sal ammoniac, 


THE GENERATION OF CURRENT 45 


forming zinc chloride, and hydrogen and ammonia 
are set free. The hydrogen is then oxidized by 
the manganese. 

These cells formerly had a wide employment, 
but with the development of the dry cell, manu¬ 
factured at so low a price that it was possible 
easily to replace the exhausted cells, they have 
rapidly fallen into disuse. Even the small amount 
of care required in filling the jars with water and 
sal ammoniac makes them less desirable than the 
dry cells, which are also more compact and less 
messy. 

Dry Cells. The cell with a liquid electrolyte 
possesses many disadvantages, not the least of 
which is its lack of portability. It was found, 
however, that it was possible to reduce the amount 
of liquid — in fact, merely to keep the materials 
surrounding the elements damp; and thus was 
developed the so-called dry cell, a name that is 
obviously a misnomer, inasmuch as there must be 
an electrolyte in the form of a moist mixture. 
In other words, we can take a zinc-carbon cell 
of the familiar Leclanche type and then reduce the 
moisture to what is merely sufficient for the elec¬ 
trolyte. If the dry cell loses water, it deterio¬ 
rates ; and also, it is as liable as are other cells to 
experience local action. 

Dry cells, with some form of connecting wires or 
conductors at the top, carefully covered, sealed, 
and wrapped, we are likely to take as a matter of 


46 


EVERYDAY ELECTRICITY 


course; and we use them in our motor cars and 
motor boats, or for our bells and other appliances, 
wherever a small source of power is needed. In 
fact, for most purposes they have entirely sup¬ 
planted the cell with the liquid electrolyte, which 
is rarely seen outside of the laboratory. 

Ordinarily, these dry cells stand about six 
inches in height, in well-sealed, firm cylinders, 

and are about two and a 
half inches in diameter. 
It is at once suggested 
that cells of this size are 
by no means all, for there 
are numerous dry cells 
available for use in pocket 
flashlights and other de¬ 
vices that are familiar in 
the last degree. Remov¬ 
ing the wrappings of such 
a cell, we find that the 
cylinder is a can of zinc, 
which forms the negative element of the battery; 
and at the top there is attached to it a thumb nut 
by which connection can be made. Within this 
can is a tube of pulpboard provided with a bottom 
that serves to insulate the zinc from the mixture, 
and also as a medium for carrying a part of the 
electrolyte. In the center of the cylinder is placed 
a carbon rod, and around this, tightly packed, is 
a mixture consisting of crushed carbon, graphite. 



Card on Fod 

\ Afeordent layer 
Pa/p Board or 
olderAfaler/a/ 

Z/nc Can 

6rana/ofed 
cordon and 
Depolarizer 


Fig. 16: Section of an Ordinary- 
Dry Cell. 

















THE GENERATION OF CURRENT 47 


manganese dioxide, zinc chloride, and ammonium 
chloride. This mixture, when moistened, forms 
the electrolyte. This material, when in place, is 
sealed with wax or pitch. 

With the small cells, such as those used for 
flashlights, a bag of muslin is employed instead 
of the pulpboard. The chemical action of the 
dry cell is about the same as that of a liquid cell 
of the Leclanche type; and the cell when new 
gives an open-circuit voltage of from 1.5 to 1.6 
volts. When short-circuited, it has a current of 
from 25 to 30 amperes. There is a slight de¬ 
crease in electromotive force when the cell is 
standing on open circuit. 


CHAPTER V 


Electrical Units and Measurements 

Exact knowledge begins only when we can 
measure a phenomenon in addition to under¬ 
standing it in other respects. Consequently, at 
a very early stage attempts were made to measure 
various manifestations of electricity. They were 
not, however, made at once and systematically; 
for in the earlier days of the science and art, con¬ 
venient units and standards were employed in 
the laboratory by various investigators. Later, 
however, international cooperation of scientific 
men and engineers ensued; and in electricity 
alone, of all the sciences and related arts, we have 
to-day a single and international system of units 
and standards. 

The Ampere. Naturally, the first feature for 
which measurement was sought was the amount 
of electricity — that is, the current passing — in 
order (as we should say to-day) to number all elec¬ 
trons in the stream. For this we have a common 
unit, the ampere. This is employed to indicate at 
some particular point in the circuit the amount 
of current that passes in the “ unit of time”, which 
in electrical work is, of course, the second. 


UNITS AND MEASUREMENTS 


49 


An electric current in every second will de¬ 
compose a certain amount of water into its ele¬ 
ments of oxygen and hydrogen. Or flowing 
through a solution of copper sulphate between 
two pieces (or electrodes) of copper, it will cause 
a certain definite amount of copper to be deposited 
on the positive electrode. In the case of zinc elec¬ 
trodes and a solution of zinc sulphate, there would 
also be the same effect with the zinc. Likewise, in 
a solution of nitrate of silver, the amount of silver 
deposited on the positive electrode depends upon 
the quantity of current; and in fact, this case 
was the practical part of the legal definition of 
the ampere, which calls for a deposit of silver 
at the rate of “1,118 millionths of a gram per 
second (0.001118). ,, 

In addition to these chemical effects, the quan¬ 
tity of current in a circuit can be determined by 
the amount of deflection of a magnet freely sus¬ 
pended at the center of the coil around which 
the current passes. Such an instrument is known 
as a tangent galvanometer, since the strength of 
current is proportionate to the tangent of the angle 
of deflection of the needle. 

The Galvanometer. The use of the tangent 
galvanometer to measure the electric current, 
depends upon the important principle, already 
discussed, that an electric current has magnetic 
effects and establishes a magnetic field in its 
neighborhood; and that consequently, if flowing 


50 


EVERYDAY ELECTRICITY 


around a coil at the center of which is a magnetic 
needle, it causes deflection of the needle. The 
galvanometer is universally employed to detect 
and measure a current, for often we desire to ascer¬ 
tain the presence of a current in a circuit, and to 
determine its direction and intensity. 

A simple and perhaps rough device that we 
might employ, is the general arrangement shown 
in the diagram (Figure 17), where the needle is 


Co/7 of///re> 



Fig. 17: A Simple Galvanometer. 

mounted on a pivot and a number of loops of 
copper wire are formed into a coil. If no current 
is passing, there is obviously no deflection of the 
needle, but a current flowing through in one direc¬ 
tion will deviate the needle to one side; and if 
the direction is reversed, to the other. 

When one is dealing with very small currents 
(and the electrician has to deal with very small 
currents quite as much as with those that operate 
lighting systems or are used in transportation), 
it is necessary to have a most delicately poised 
needle. Accordingly, the needle is suspended by 















UNITS AND MEASUREMENTS 


51 


a fine fiber of silk or quartz; and in order that 
the observer may tell whether it moves or not, 
a mirror is employed in connection with it. As 
the needle moves, the mirror reflects a beam of 
light, so that for the observer the movement will 
be magnified many fold. Not only do we make 
the needle light and slightly magnetized, but by 
using fine wire we are able to secure many turns 
in the coil or coils, so that our galvanometer will 
give a visible indication when only a very feeble 
current flows. 

So we have various arrangements of coils and 
needles. In fact, to get a weak needle-effect, 
several magnetic needles are used together with 
poles reversed, and as a result we have a galva¬ 
nometer that will show the most minute currents. 

In what is known as the d ’Arsonval galvanom¬ 
eter, a group of permanent horseshoe magnets 
is arranged horizontally, and between the poles of 
the magnets is suspended a rectangular coil of 
fine copper wire through which the current to be 
measured passes. There may be the arrange¬ 
ment of mirrors and scale mentioned above; but 
what is more usual, the instrument can be made 
considerably more robust, and the suspended coil 
be made to come to rest much more quickly, or 
in short, become “ deadbeat ” or “ aperiodic.” 

The Ammeter. This idea can be carried farther 
in the portable galvanometer, where, instead of a 
suspension for the coil, jewelled or other fine bear- 


52 


EVERYDAY ELECTRICITY 


ings are used, and the rotation of the coil is 
against the action of a spiral spring. Not only 
can such a device be used to detect a current, but 
now it is made with such precision that it forms 
an accurate means to measure current by the aid 
of a thin pointer on a direct-reading scale. 



Correct Arrangement of Ammeter-/a Series 



Wrong Arrangement-Ammeter as a stunt 
short c/rcu/ts the Generator 


Fig. 18: (Above) Ammeter to measure current, inserted in series in a cir¬ 
cuit including generator G and external resistances. (Below) Ammeter wrongly 
placed in a circuit as a shunt. Having a small resistance, the ammeter will 
short-circuit the generator. 

An ammeter should always receive careful 
treatment and be connected properly in the cir¬ 
cuit, with due regard for the polarity marked on 
the binding posts. The ammeter is connected 
in the circuit in series — that is, the current pass¬ 
ing through it goes through lamps, motors, etc., 
whereas the voltmeter, to be described below, is 
always a shunt. 







UNITS AND MEASUREMENTS 


53 


A simple form of ammeter, and one that can be 
readily constructed, consists of a coil in which is 
suspended a soft iron vane or plunger. Naturally, 
the greater the current flowing in the coil, the 
greater will be the attrac¬ 
tion for the soft iron, which 
will be drawn into the coil 
against the action of a 
spring or of gravity. Such 
a meter, when calibrated, 
may be used for either 
alternating or direct cur¬ 
rent. 

Heating a metal natu¬ 
rally produces expansion 
in it; and by some me¬ 
chanical device, which in¬ 
cludes a moving pointer 
and scale, this expansion 
can be measured and indi¬ 
cated, the amount vary¬ 
ing as the square of the 
current. The hot-wire 
ammeter also can be used 
for both alternating and direct-current measure¬ 
ments, and it is employed extensively in radio work. 

The Voltmeter. Now, the ammeter, which has 
a very small resistance (say, about .001 ohm), 
measures the current. If we not only measure the 
current but also employ a resistance whose amount 


■spend/np 

*5pr/np 



M'msibrcumerrt 
to be measured 


Fia. 19: A Simple Form of 
Ammeter. 





















54 


EVERYDAY ELECTRICITY 


we know, then by Ohm’s law, later explained, 
we get the electromotive force; for Electromotive 
Force = Current X Resistance. Consequently, 
when a resistance sufficiently higher, as com¬ 
pared to any possible external circuit, is used, 
the electromotive force is proportional to the 
current and can be indicated by the pointer 
and scale. Thus we have a voltmeter, which al¬ 
ways is used as a shunt and receives only a small 



Fig. 20 : Circuit from a continuous-current generator when a voltmeter is 
used to measure the drop of potential, first, at the generator, and then at the 
successive resistances A, B, and C. The fall of potential in a circuit is propor¬ 
tional to the resistance across which it is measured. 

part of the current, so that we can place it across 
any interval where we desire to determine the 
difference in potential; as, for example, in the 
diagram (Figure 20), where it may be desired to 
know, in the first case, the potential difference 
across the generator G, or the drop in potential 
at the elements of the line A, B , and C , which 
may be incandescent lamps or any devices in use. 

The voltmeter may be of different forms, rang¬ 
ing from the large instrument mounted in the 








UNITS AND MEASUREMENTS 


55 


power house to the small affair on the instrument 
board of the motor car to indicate the functioning 
of the storage battery or the generator. There 
are also millivoltmeters, in which the scale is 
graduated in thousandths of a volt, just as there 
are also milliammeters. 

Resistance. If our electric circuit is such that 
conditions act to hinder the passage of the elec¬ 
trons, there will be a smaller number moved in 
unit time, and hence the stream or current will 
be correspondingly reduced. This hindering of 
the passage of the electrons is known as resistance, 
and is a very important item in all electrical work. 

Ordinarily, we think of metals as the more usual 
conductors, and a table of conductivity would 
run somewhat in the following order: Silver, 
copper, gold, aluminum, platinum, iron, lead, 
mercury, selenium, and carbon. On the other 
hand, substances possessing high resistance or poor 
conductivity would be glass, porcelain, mica, 
asbestos, shellac, india-rubber, oils (such as par¬ 
affin and other petroleum products), and paper 
and other natural and prepared cellulose sub¬ 
stances — dry wood being typical of the natural 
sort. 

For many purposes, in conveying the current 
a metal wire is a definite form of conductor and 
is extensively employed, so that we can consider 
its property of electrical resistance. The first 
consideration is its material; and it will appear at 


56 


EVERYDAY ELECTRICITY 


the outset that the substances listed above vary 
widely, differing in their resistivity or specific 
resistance for the same dimensions and conditions. 

We commonly refer to resistance in terms of a 
wire conductor, as this is easier to visualize, but 
all substances must have resistance; including 
liquids, such as the electrolyte of a battery, or such 
a material as vulcanite — to mention a well- 
known insulator with high resistance. 

The Ohm. Naturally, for resistance we must 
have a unit; and this unit is taken as the ohm, 
realized in a standard in the form of “ the resist¬ 
ance offered to an unvarying electric current by 
a column of mercury at the temperature of melt¬ 
ing ice, fourteen and four thousand, five hundred 
and twenty-one ten thousandths (14.4521) grams 
in mass, of a constant cross-sectional area, and of 
the length of one hundred and six and three tenths 
(106.3) centimeters.” The required apparatus 
is found only in national physical laboratories 
or special research or precision laboratories; but 
in actual practice, the ohm is realized by some 
form of coil wound with metal wire. This changes 
but little with variation of temperature, and will 
reproduce with high accuracy the resistance of the 
mercury column and serve as a secondary stand¬ 
ard. The resistance represented by an ohm can 
perhaps be visualized by means of the statement 
that one thousand feet of Number 10 soft copper 
wire have a resistance of approximately one ohm. 


UNITS AND MEASUREMENTS 


57 


The Volt. Obviously, if the electrons at one 
terminal preponderate in amount over those at 
the other, there will be a flow to restore equilib¬ 
rium. This will force a passage from the electrode 
where there is a surplus; and the measure of that 
tendency to flow we term voltage or electromotive 
force, which is comparable with pressure or 
“ head ” in hydraulics. By voltage, or difference 
in the potential, is understood this difference in 
condition between the two points under considera¬ 
tion ; and this is measured in volts. 

Now, the volt also is a practical unit that has 
been evolved by physicists, and it represents very 
nearly the difference of potential existing in the 
Daniell cell or in the familiar bluestone gravity 
cell of the country telegraph office. In practice, 
the volt is realized, according to the legal defini¬ 
tion, as the electromotive force that, steadily 
applied to a conductor whose resistance is one 
international ohm, will produce a current of an 
international ampere, and is practically equivalent 
to of the electromotive force between the 

poles or electrodes of the voltaic cell known as 
Clark’s cell at a temperature of fifteen degrees 
centigrade (15° C.) and prepared in the manner 
described in the standard specifications. 1 

1 The United States Bureau of Standards and similar institutions 
in Europe now employ as a standard the Weston normal cell, and, 
by intercomparison and otherwise, carefully maintain the value of 
the volt. The accepted value of the volt in terms of the Weston cell 

is 


1.01830 




58 


EVERYDAY ELECTRICITY 


Ohm’s Law. Having these three fundamental 
units, we are prepared to understand the underlying 
relation as expressed in Ohm’s law. This simple 
mathematical expression states that with a con¬ 
stant unidirectional current, E = IR, where E is 
the electromotive force, I the intensity of the 
current, and R the resistance. In other words, 
where the resistance is constant the current will 
vary as the electromotive force. This formula 


can be stated also as I = § ; or, in terms of the 

J ±v 

units just defined, Amperes = 

It takes but little appreciation of mathematics 
to realize that here we are told that the current in 
the circuit will increase with the electromotive 
force, and will diminish as the resistance becomes 
greater. With twice the electromotive force, we 
shall have twice the current; but with twice the 
resistance, only one half the current. Likewise, if 
we cut down the resistance, we increase the current. 

A simple way, for example, of cutting down 
the resistance is to use two similar conductors, in 
parallel, in place of one, thus doubling the path 
for the current and permitting twice as much to 
flow. When we have a fixed source of electro¬ 
motive force (or voltage), such as the electric- 
light service or dry cells, the amount of current 
must be regulated entirely by the resistance in 
the circuit. For example, on a 110-volt lighting 



UNITS AND MEASUREMENTS 


59 


circuit, an incandescent lamp is inserted with a 
resistance of 300 ohms. Obviously, such a lamp 
will take 0.366 of an ampere of current. 

Again, on a circuit of 6 ohms resistance we may 
need a current of 2 amperes; and the problem be¬ 
comes : How many dry cells, each of 1.5 volts, will 
be required? The answer is that we shall need 



12 volts; and as each cell gives 1.5 volts, eight 
cells will be required. 

A practical example, as shown in the diagram 
(Figure 21), is furnished by a generator that de¬ 
livers current with a voltage of 120 volts at its 
terminals. The generator has an internal re¬ 
sistance of 1 ohm, and in the circuit are resistances 
of 8 ohms and 11 ohms. The total resistance, 
therefore, is 20 ohms; so that the current in the 
circuit would be 6 amperes. 

The Watt-hour Meter. So far, the measuring 
instruments we have described are found in the 
laboratory or central station, or are carried about 






60 


EVERYDAY ELECTRICITY 


by the electrician for his testing; but when we 
come to measure electrical energy, we find an in¬ 
strument that is familiar and may be observed 
by a trip to the cellar or a short climb on a step- 
ladder. Whereas the wattmeter measures the 
rate of doing work and indicates the horsepower 
or number of watts (that is, the consumption of 
energy in the circuit), the watt-hour meter of the 
public service company measures the actual con¬ 
sumption of electrical energy for which we must 
pay. 

The unit employed in the United States for 
this measurement of energy is the watt-hour, or 



KILOWATT HOURS 


Fio. 22: A Dial of a Watt-hour Meter. — The reading here shown is 538 
kilowatt hours. An ordinary household meter of this type should be correct 
within one per cent. 

the rate of doing work represented by one watt 
maintained for one hour; and in ordinary com¬ 
mercial usage, the kilowatt-hour, meaning one 
thousand watt-hours, is employed as the unit. 
One horsepower is equal to 746 watts; so that, 
roughly, one kilowatt is equal to 1^ horsepower. 

The watt-hour meter is essentially a small 
electric motor driving a series of gears with num¬ 
bered dials, to indicate the number of revolu¬ 
tions of the armature or disc. These meters 


UNITS AND MEASUREMENTS 


61 


are of various forms, being either of the commu¬ 
tator type, mercury-flotation type, or induction 
type, depending upon the current and the system 
of lighting employed. There is also a brake sys¬ 
tem, composed of a disc of nonmagnetic material 
mounted on an armature spindle, and rotating 
between the poles of one or more permanent mag¬ 
nets, so as to reduce the motion. The usual 
arrangement is to have one winding, which is 
called the potential coil, connected as a shunt 
across the circuit where the load is being measured ; 
and the other winding, called the current coil, 
connected in series with the load. The principle 
of operation is that the torque or power of revo¬ 
lution exerted by the motor varies with the aver¬ 
age power consumed, so that the speed of the ro¬ 
tating disc is proportionate to the average power 
taken; and the total number of revolutions which 
the disc makes during any interval will depend 
upon the energy consumed during this interval, 
irrespective of whether the power remains con¬ 
stant or not. 


CHAPTER VI 


Induced Currents 

The experiment of the current flowing over a 
compass needle indicated that the current pro¬ 
duced a magnetic field. Conversely, then, a 
magnetic field should produce a current; and a 
few simple experiments will show that a moving 
magnetic field actually does produce a current. 
Furthermore, on this property is based the pro¬ 
duction of current in large amounts by induction 
coils, magneto-machines and other generators, 
and both direct and alternating-current dynamos. 

This phenomenon may be shown experimentally 
by employing our galvanometer as a detector of 
current. We take an insulated copper wire and 
wind it in the form of a cylindrical coil (such as 
we used for our electromagnet), which is called a 
solenoid. Again we use the coil instead of a single 
conductor to increase the strength of the magnetic 
field, as the intensity of the magnetic field at the 
center is proportional to the number of turns per 
unit length of the solenoid. Then we connect 
its end with the terminals of the galvanometer. 
Now let us take a bar magnet and insert it within 
the coil, observing that the galvanometer needle 


INDUCED CURRENTS 


63 


moves as the magnet is introduced within the coil; 
and that after such movement it will assume a 
position of rest, showing that no current is then 
flowing through its coils. Then let us withdraw 
the magnet, and there will be noticed another 
deflection of the needle, equally sudden but in 



Fig. 23: Induced current ia produced by a magnet introduced into a solenoid. 

the opposite direction. This movement will take 
place irrespective of which pole of the bar magnet 
is introduced within the coil. 

Naturally, if we hold the magnet still and move 
the coil towards or from its poles, the result will be 
precisely the same; and the fact is unmistakable 
that a current is produced whenever there is 
motion between a magnetic field and a conductor 
that forms a closed or complete circuit. If the 























64 


EVERYDAY ELECTRICITY 


conductor be arranged in the form of a loop and 
its motion be rotary rather than rectilinear, then 
we have the germ of the modern dynamo. 

The more intense the magnetism, the stronger 
will be the current; and the difference of potential 
produced will depend upon the speed with which 



Fig. 24 : Induced current is produced in the adjoining coil B by the 
motion of a coil A carrying a current. 


the conductor is moved across the magnetic field, 
and also, if there is more than one turn, upon the 
number of turns in the moving coil. 

Now let us take a coil or solenoid carrying a cur¬ 
rent ; and calling it our primary coil, let us use it 
in place of the bar magnet in our recent experi¬ 
ment. When the small coil is inserted within, 







































INDUCED CURRENTS 


65 


or withdrawn from, the large coil (now known as 
the secondary), the movement will cause a de¬ 
flection of the galvanometer similar to what we 
previously noticed. But it will be said: Why 
move the primary coil at all, when you can leave it 
permanently within the secondary, and by means 
of a switch in the circuit that supplies it with 
current can permit the electricity to flow or cut 
off the flow at will — thus causing the magnetic 
field to pass through the windings of the second¬ 
ary, just as if you inserted and withdrew the 
small coil ? 

When the circuit is closed in the primary, the 
windings of the secondary are cut by the mag¬ 
netic field, and there is generated a current in the 
secondary. When the circuit is opened, a similar 
effect takes place, only the current is in the oppo¬ 
site direction, as shown by the galvanometer. 

What has happened is that the current has been 
produced by induction; and the arrangement of 
the two coils just referred to is a simple induction 
coil. By properly disposing the turns or windings 
as regards their number and nature and the current 
employed, it is quite possible to produce any elec¬ 
tromotive force desired; that is, a low potential 
may be built up into one much higher, or vice 
versa , as we shall find done in the transformer. 

The diagram (Figure 25) shows the arrange¬ 
ment of an induction coil, which should readily 
be recognized from the indication of the primary 


66 


EVERYDAY ELECTRICITY 


and secondary coils and the battery; but there are 
a few adjuncts that perhaps should be explained. 
We have tried to emphasize the fact that the vol¬ 
tage in the secondary is produced only when the 
main current is made or broken. Consequently, 
to obtain a frequently interrupted current, such 
as is needed for igniting the spark on a motor-car 


i Spark Gap 



Fig. 25: Diagram of an induction coil with interrupter and condenser. 


engine, or is employed in a medical battery, some 
mechanical “ break ” arrangement must be used; 
a simple and familiar one being here illustrated. 

The primary is wound around a core of soft iron 
in order to secure a stronger magnetic field by 
furnishing for the lines of force a path that they 
will traverse more readily than they will air; and 
this core becomes magnetized when the current 
from the battery flows through the circuit. This 






























INDUCED CURRENTS 


6? 


magnetization attracts the soft-iron armature at¬ 
tached to the spring; but as the armature moves, 
the circuit is broken, and the armature flies back 
to its original position to repeat the succession of 
operations. In other words, we have here pro¬ 
duced an alternating current in the secondary, 
which usually consists of a large number of turns 
of fine wire, whereas the primary consists of a few 
turns of heavy wire. It follows, therefore, that 
an interrupted current in the primary will produce 
in the secondary a high voltage, which will be indi¬ 
cated by a spark at the gap between the balls 
in the diagram, or at the spark plug in the case 
of the motor-car engine. 

But it must not be inferred that because the 
voltage has been increased from that of a few wind¬ 
ings to an amount capable of supplying a brisk 
spark, there is any increase in the amount of work 
done. The current in the primary may be fairly 
large, but the voltage is low. On the other hand, 
the current in the secondary is very small, but its 
voltage is high. 

Let us take another instance of induction, the 
reverse of the foregoing. Let us have an alter¬ 
nating current of high potential generated at a 
central station. Let this current flow around the 
fine winding of what is known as a transformer; 
then from the adjoining coil of coarse wire will 
be drawn a current of low voltage, suitable for 
household lamps and motors. The interruptions 


68 


EVERYDAY ELECTRICITY 


or alternations in such a current are produced by 
the generator, so that there is no need of any 
special device at the coils, which can be arranged 
around a common core made of laminated iron 
and of the general shape indicated in Figure 26. 



Inductance or self-induction is an important 
property of a circuit or a conductor, by virtue 
of which an electromotive force produced in a 
conductor by the varying magnetic flux is gene¬ 
rated upon the closing of the circuit and likewise 
by the corresponding change when the circuit is 
open. If we have a coil in the circuit as shown 
in the diagram (Figure 25), it will be apparent 
that the magnetic field built up around the wire 
will pass through the loops of such a coil; or in 
other words, we have a conductor cut by a field 
of magnetic force, and a voltage produced. 

The current will thus act inductively on itself; 
and naturally, if there are many turns in the coil, 
the effect will be greater. Likewise, if the coil 
has an iron core (as in the case of the induction 














INDUCED CURRENTS 


69 


coil just described), there will be a greater mag¬ 
netic flux through the coils. Now, the electro¬ 
motive force or voltage thus induced will be oppo¬ 
site to the action or current that produces it, and 
consequently it will act to oppose the flowing 
of the current. Accordingly, when a circuit is 
closed, the current does not rise at once to its 
full value, but increases slowly, whereas at the 
opening of the circuit the induced voltage may be 
sufficient to produce a spark or arc across the gap 
at the key or switch where the circuit is opened. 

The inductance is strongest in the case of a coil 
of many turns, but it is also to be encountered in 
a straight wire, such as a telephone or submarine 
cable. The usual way to avoid self-induction is 
to wind half the coil in one direction and half in 
the opposite direction, which may be done by 
doubling the wire to be wound in one direction. 
The effect of inductance is very marked in the 
case of an alternating current, as the greater the 
number of the alternations, the greater will be 
the induced voltage. Consequently, it is possible 
to provide a coil with an iron core having so much 
inductance that alternating or varying currents 
of high frequency cannot pass. This finds ex¬ 
tensive application in telephony, as later we shall 


see. 


CHAPTER VII 


Storage Batteries 

The so-called storage cell, secondary cell, or 
accumulator, finds a wide range of application, 
and is familiar by its use on a motor car or with a 
radio receiving set. An accumulator or secondary 
cell is essentially a voltaic couple which originally 
started with plates or elements of the same ma¬ 
terial, but which are so changed by electrolysis 
on charging that they will function as an ordinary 
voltaic cell and deliver a constant current. 

The action in the storage cell consists of (a) the 
separation of various chemicals by electrolysis 
during the process of charging; and when the 
charging current is removed and the circuit is 
closed, of ( b ) a re-combination in which a dis¬ 
charge current is given off almost equal to the 
charging current. In a storage cell, the positive 
plate is the one out of which the current flows on 
discharge, and the negative plate is the one into 
which the current flows. 

The Lead Battery. The action of a storage cell 
can best be explained by taking a typical lead cell, 
which consists of two plates of lead sulphate im¬ 
mersed in a solution of sulphuric acid. This 


STORAGE BATTERIES 


71 


solution is the electrolyte, and with regard to its 
strength and quality must be carefully tested, as 
by the hydrometer. From some outside source 
of electric energy, such as a generator, a current is 
passed through such a cell and it is then found 
that the two plates, originally of the same material, 
have been changed — that the cathode has become 
lead peroxide and the anode metallic lead. If, 
after this transformation has taken place and the 
charging current has been removed, the two plates 
are joined, the current will flow from the peroxide 
plate to the metallic lead plate; and in the course 
of this action the two plates will be transformed 
back into the original lead sulphate from which 
they started. 

In the case of the lead battery, the positive 
plate is the one on which lead peroxide is formed, 
and has a hard surface of a reddish-brown or choco¬ 
late color. The negative plate is of a grayish 
color and carries the sponge lead with a much softer 
surface. 

Forming the Plates. There are two main types 
of lead cells: the Plante type, and the Faure, or 
pasted, type. The Plante type, which is the 
simpler form, has its plates prepared or formed 
by the action of the current — namely, by re¬ 
peated charging and discharging; so that the lead 
sulphate is effectively realized, and a cell with an 
electromotive force of about two volts is developed. 
The Plante type starts with a pure lead plate of 


72 


EVERYDAY ELECTRICITY 


large superficial area, made in various forms of 
corrugation and otherwise. For example, the 
central lead pattern consists of a solid sheet of 
pure lead on which ribs are formed; the cast- 
lead pattern has various ribs made in the plate; 
and in the composite or pellet pattern the plate 
is made by forcing small pellets or buttons into 
circular openings in a grid composed of a hard 
lead-antimony alloy. The Plante type has con¬ 
siderable weight to its plates, which also possess 
bulk; and therefore it is not available where 
weight and space are important considerations. 

Pasted Plates. Naturally, to form plates in the 
way outlined required considerable time and ex¬ 
penditure of current. Therefore the Faure method 
was devised of preparing the plates by using 
oxide of lead on their surface at the very beginning. 
The first step in forming these plates is to employ 
the positive plate as a unit, and let the charging 
current oxidize its surface into lead peroxide, 
while the negative plate is charged in the usual 
way by transforming the lead oxide to sponge lead. 
The oxide of lead, in the form either of litharge or 
lead monoxide (PbO) or of red lead (Pb 3 0 4 ), is 
made into a paste and is applied to the grid in 
various ways. 

Typ es of Storage Batteries. One of the most 
marked developments in pasted-plate storage 
batteries is found in the so-called “ ironclad bat¬ 
tery.” This aims to do away in part with the 


STORAGE BATTERIES 


73 


shedding of the material on the positive, lead-per¬ 
oxide plate; this being ordinarily a weak feature 
of the pasted-plate battery. In the “ ironclad ” 
form, the positive has lead peroxide packed into a 
vulcanite tube perforated with small openings for 
the passage of the current. Through the center of 
each tube runs a rod of lead for the contact. It 
is claimed that such a positive plate has a longer 
life than has the ordinary pasted plate. 

Another type of battery seeks to protect the 
peroxide from shedding by the use of solid rubber 
containers, which are somewhat simpler and are 
thought to afford life as long as that of the battery 
just described. There has been also a tendency 
recently to make batteries with very thin plates, 
which will give 50 to 200 per cent, output per unit 
of weight and have a longer life. The plates in 
such batteries are only one thirty-second of an 
inch thick, and they can be so assembled as to 
make buckling impossible. 

The battery plates and electrolyte may be 
installed in hard-rubber jars. These are used for 
vehicles and for portable batteries, the plates 
being supported on ribs at the bottom of the jar. 
This arrangement affords sufficient space for the 
material that falls away from the plates. Such 
rubber jars are usually covered tightly in order to 
prevent the sulphuric acid from being spattered. 

For permanent installations, glass jars are 
usually employed, but their use is restricted to 


74 


EVERYDAY ELECTRICITY 


the small sizes on account of the larger ones being 
liable to break, due to strain set up in the glass 
after annealing. For the very large batteries, 
tanks of wood lined with lead are used and 
great care is required in making all connections 
tight. 

The Alkaline Storage Battery. While the vari¬ 
ous types of lead storage battery have been in gen¬ 
eral use, from time to time efforts have been made 
to secure a storage cell of lighter weight. The al¬ 
kaline type of Edison has an iron-nickel element 
immersed in a solution of caustic potash; the posi¬ 
tive plate being formed of nickel hydroxide for its 
active material, and the negative of iron. On 
the discharge of this cell, the iron is oxidized and 
the nickel hydroxide is reduced to nickel sesqui- 
oxide (Ni 2 0 3 ). The essential reaction that takes 
place is a transfer of the oxygen between the two 
electrodes, forward and back on charge and dis¬ 
charge. The positive or nickel plate is made up of 
perforated steel tubes, nickel-plated, which are 
filled with alternate thin layers of nickel hydroxide 
and pure metallic nickel. Each tube is reinforced 
with steel bands and is flanged so that it is carried 
by a steel supporting frame or grid, which is also 
nickel-plated. The negative plate consists of a 
grid of cold-rolled steel, nickel-plated, in which 
are a number of nickel-plated pockets of finely 
perforated steel, filled with powdered iron oxide. 
These elements are contained in a jar made of 


STORAGE BATTERIES 


75 


sheet steel, nickel-plated, and they are grouped 
together in the usual way. 

Applications of Storage Batteries. The storage 
battery finds extensive application in the central 
station as an emergency reserve; and in such 
stand-by service, batteries of large capacity are 
employed. Likewise, on electric railways storage 
batteries are employed to regulate the load on the 
line and to meet requirements when there is a 
severe strain on the generating apparatus. 

One of the most important applications of the 
storage battery is to railway-car lighting; the 
batteries being charged by a generator either at 
the locomotive or (as is more usually the case) 
driven from the axle of the car. Consequently, 
when the car is at rest, the storage battery carries 
the entire load. When the car is in motion, the 
battery may be switched on and off automatically 
as conditions warrant, thus keeping the supply 
constant and delivering the current to the lighting 
system of the car at about 30 volts. 


CHAPTER VIII 


Generators and Motors 

In the development of electricity by friction and 
by chemical action, it is readily realized that the 
amount of energy transformed and made available 
is comparatively limited. This fact was appre¬ 
ciated by the earlier experimenters and interfered 
materially with the development of useful applica¬ 
tions. The great weight of the cells, the rapid ex¬ 
haustion, and the inconvenience of the liquid 
electrolyte were but a few of the causes restricting 
work in this field. 

It was found, however, that by a suitable con¬ 
trivance mechanical energy could be transformed 
into electrical energy. Once this was accom¬ 
plished, adequate current supplies were available, 
not only for experiment but for industrial and 
other practical uses ; and soon they were applied 
to lighting and transportation. 

To realize just what is involved in the modern 
dynamo or generator, it is convenient to study 
first the magneto, a machine in which there are one 
or more permanent magnets, usually in horseshoe 
form, so that the lines of force are connected and 
continuous. In the diagram (Figure 27 ), the lines 


GENERATORS AND MOTORS 


77 


of force are indicated by the lines traversing the 
space between the north and south poles. A wire 
is arranged in the form of a loop, so as to rotate in 
the gap between the two poles of the magneto, 
transversely to the magnetic lines of force. In the 
arrangement given in the diagram, the two dots 




Fia. 27: A Simple Magneto. — (A) Side view and ( B ) top view. 

W and W 1 indicate the wire; and looking at this 
arrangement from the top, as at B , we see that 
our loop of wire or conductor has its ends con¬ 
nected with two rings (indicated by r 1 and r 2 ) 
mounted on the axis of rotation. In contact with 
the two rings are two copper brushes hr x and br 2f 
and from them the conductors lead to the ex¬ 
ternal circuit. 

The wire, as it is turned, will cut the lines of 
magnetic force and thus establish a difference of 
potential, so that, expressed in the conventional 
way, there will be a current flowing in the loop away 
from the observer who looks at the end in diagram 











































78 


EVERYDAY ELECTRICITY 


W 


A, and from left to right in the top view B ; and 
so that r 2 will be at a higher potential than r l9 the 
other extremity of the wire. In other words, the 
current will flow between r 2 and n and will be 
drawn off by the brushes at bri and br 2 . 

After the loop has made a half-revolution, the 
position of its two elements is reversed, and the 
direction of the flow of current will be opposite to 

what it was be¬ 
fore. In other 
words, as the 
loop is rotated 
in the mag¬ 
netic field and 
cuts the lines 
of force, there 
will be pro¬ 
duced in it an ordinary alternating current — one 
that flows alternately in one direction and then in 
the other. 

Now, instead of the one wire and one loop here 
shown for purposes of explanation (as is the usual 
practice), many wires and many turns are em¬ 
ployed in the form of an armature coil or bobbin. 
The voltage produced by the successive action of 
the turns is made higher; and the modern 
machine also may have an induction winding that 
gives a spark of high potential. Thus equipped, 
and of course with minor but substantial improve¬ 
ments, the magneto is widely employed. 





Fig. 28 : Diagram of a rotating conductor loop and 
of collector rings and brushes. 






GENERATORS AND MOTORS 


79 


W 


The Direct-current Generator. The first experi¬ 
menters with the magneto-machine found that per¬ 
manent magnets of horseshoe shape would afford 
only a limited current, and accordingly these were 
replaced by electromagnets, the result being the 
dynamo. A battery was used to excite what are 
known as the field magnets, and later the current 
thus generated was sent through the field coils, 
magnetizing the poles without the use of the bat¬ 
tery. It was realized that in this way a dynamo 
or generator could be developed with almost no 
limit to its size. 

The Commutator. For many purposes, the 
electric current is desired to flow continuously 
in one direction, as 
does that from the 
voltaic battery. 

This is accom¬ 
plished by means 
of a commutator, a 
device to be found 
at the point where 
the copper or carbon brushes take off the current 
for the external circuits. Here, in place of the two 
rings of Figure 28, may be substituted (Figure 29) 
a single split ring, divided into two segments, to 
which the two terminals of the rotating conduc¬ 
tor are connected, W to segment r\, and W l to 
segment r 2 . Now, the brushes br x and br 2 are 
arranged diametrically opposite, so that they 







Fia. 29 : Diagram of a rotating conductor 
loop, with commutator. 








80 


EVERYDAY ELECTRICITY 


take the current from the two segments; but as 
the shaft revolves and the brushes slip from one 
segment of the commutator to the other, at this 
instant the connection of the coil with respect to 
the external circuit is reversed, so that the direc¬ 
tion of the current flowing in the external circuit 
is always the same; hence, likewise, the cur¬ 
rent taken from the segments is always flow¬ 
ing in one direction. This intermittent, unidirec¬ 
tional current, if used in an incandescent lamp, for 

example, would cause flickering if 
the speed of rotation were not fast. 

The loop or conductor that is 
rotated in the magnetic field be¬ 
tween the poles of the field magnet, 
and is termed the armature, actu¬ 
ally consists not merely of the single 
loop referred to but of many con¬ 
ductors, carefully insulated, one 
from the other and all from the 
laminated core of soft iron that 
The core forms a part of the mag- 
This armature is revolved by the 
application of some outside energy, such as a 
steam engine or a water wheel. 

Practically, in place of the two rings already 
referred to, the commutator is made up of a series 
of copper segments, each segment being insulated 
from its neighbors, and from the frame of the 
machine. The wires of the armature windings 



Fio. 30: Diagram 
of a simple commuta¬ 
tor, with brushes. 


carries them, 
netic circuit. 


GENERATORS AND MOTORS 


81 


(that is, the terminals of the various loops) are 
connected to segments just opposite to each other, 
being so arranged that as each segment passes the 
brushes, one brush, such as br u is constantly kept 
positive and the other, 6r 2 , negative; and conse¬ 
quently the current, although it may be intermit¬ 
tent, is a direct current — that is, it flows in a single 
direction, as does the current from the voltaic cell. 

If, in a direct-current dynamo, the current taken 
off the commutator passes directly around the 



Fig. 31: Arrangement of windings in three types of continuous-current 

generators and motors. 

field coils, we have what is known as a “ series- 
wound” dynamo. If, on the other hand, the field 
coils are connected directly across the brushes, 
then the machine is said to be “ shunt-wound ”; 
and a combination of both principles gives a 
“ compound-wound ” dynamo. 

Early in the use of the dynamo, it was found 
that by adding more poles to the dynamo its ca¬ 
pacity was increased. Generators or motors may 
have as many as twenty-four poles. 


























































82 


EVERYDAY ELECTRICITY 


At first, the generator was driven by a belt from 
an engine flywheel; but in the interest of mechani¬ 
cal efficiency this was replaced by units in which 
the armature was “ direct-connected ” to the en¬ 
gine shaft. Later, it was found that with recipro¬ 
cating engines of sufficient size to run large 
generators, the necessary high speed could be 
obtained only at a prohibitive cost. With slow 
engine speeds, the capacity of generators and al¬ 
ternators was limited by size. High-speed ma¬ 
chines could be made much smaller; and in general, 
size varies inversely as speed. To-day, a steam 
turbine is generally used at all modern central 
stations, direct-connected to what is known as a 
turbogenerator. Where water power is available, 
the usual arrangement is to have a hydraulic tur¬ 
bine, or other water wheel, direct-connected to a 
generator, and such units are now extensively 
used. 

Direct-current Motors. In the direct-current 
generator, mechanical energy is transformed into 
electrical energy; in the motor, the operation is re¬ 
versed and a current of electricity is sent through 
the armature and field coils of the machine. The 
force acting between the current-carrying con¬ 
ductor and the magnetic field causes the armature 
to rotate and supply mechanical power. Theoreti¬ 
cally, any direct-current generator can be used as a 
motor, though of course better results are obtained 
with machines designed for the special functions to 


GENERATORS AND MOTORS 


83 


which they are to be devoted. The self-starter of 
many motor cars, however, comprises an inter¬ 
changeable machine. 

This action of the motor is shown in the diagram 
(Figure 32), where an electromagnet is so mounted 
that it can turn between 
the four magnetic poles 
shown. By means of a 

commutator, the direc- - 

tion of the current in the ^ 
electromagnet can be re¬ 
versed so that a north 
pole, as n, may become a 
south pole when it reaches Fla. 32: Poles and Armature of a 

Direct-current Motor. 

a position opposite S. 

Consequently, it is first repelled from pole N and 
attracted to pole S, and so on. The opposite 
pole is treated in a similar way. 

Advantages of Direct-current Motors. The di¬ 
rect-current motor possesses many advantages that 
lead to its wide use, particularly under conditions 
where there is considerable variation in load, in 
speed (from very slow to high), and in voltage. 
Furthermore, direct-current motors are made in a 
wide range of capacities, from the smallest dental 
motor to that of the largest electric locomotive, or 
one used in the steel mill. 

Types of Direct-current Motors. The direct-cur¬ 
rent motor is made in three leading types, the same 
as the direct-current generator, namely : the shunt 







84 


EVERYDAY ELECTRICITY 


motor, the series motor, and the compound motor; 
and the diagrams shown on page 81 apply equally 
well here. In the shunt motor, which is employed 
for driving shafting, machine tools, blowers, re¬ 
ciprocating pumps, small machinery, and motor 
generators, the field coils are arranged as a shunt 
to the armature, as shown in Figure 31. In the 
series motors, which are extensively used in rail¬ 
way and other transportation service, and for 
hoists, cranes, and similar apparatus, the arma¬ 
ture current flows through the field coils. In the 
compound motor, which is a combination of the 
shunt and series principles, an arrangement is pro¬ 
vided which is particularly useful for elevators, 
hoists, and machinery that requires frequent start¬ 
ing, particularly in tools such as punch presses. 

When the capacity of the motor is less than 5 
horsepower, a bipolar arrangement is used; but 
for greater capacity, four or more poles are em¬ 
ployed, depending upon the size and nature of the 
service. The direct-current motor can be reversed 
by changing the direction of flow in either the field 
or the armature winding, but not in both; and 
the speed control can be effected by increasing or 
decreasing the current in the field coils. 

Regulation of a Motor. The regulation of a di¬ 
rect-current motor is a very simple matter and is 
one of the strongest points in its favor, inasmuch 
as a wide range of speed can be obtained, from 
a simple turning over of the armature up to the 



General Electric Company’s Type of Street-Railway Motor, from the 

Pinion End. 



Westinghouse Squirrel-Cage Induction Motor. 
ELECTRIC MOTORS 








GENERATORS AND MOTORS 


85 


capacity of the motor. This regulation, as well as 
the starting itself, is done at the starting box or 
auxiliary rheostat, a series of resistance coils in 
which the voltage is reduced and the circuit is 
opened and closed. As soon as the circuit is com¬ 
pleted for starting, a diminished voltage is impressed 
on the motor, and sufficient current flows to start 
it; the motor runs at low speed and generates only 
a fraction of its final counter electromotive force. 
Gradually resistance in the box is cut out until 
the motor runs at full 
speed. The diagram shows 
a starting resistance and 
rheostat from which the 
successive amounts of re¬ 



sistance 7*1, 7*2, 7*3, 7*4, and ©o 

7*5, included in the circuit F™- 33 : A Starting Switch for a 

07 Direct-current Motor. 

when the starting switch 

S is placed at point 1, are successively cut out, 
until, when the switch is at point 6, the full vol¬ 
tage is applied to the motor. 

The Alternator. Having discussed the direct- 
current generator and motor, let us consider the 
alternator and the alternating-current motors, 
now widely used in many forms. Once more we 
turn to the fundamental diagram (Figure 27) and 
the explanation of the magneto, which, as we have 
said, supplies alternating current. Here the cur¬ 
rent set up in the rotating coil or loop of the simple 
alternator, cutting the magnetic lines of force as 




86 


EVERYDAY ELECTRICITY 


shown in the diagram, is reversed twice during 
each revolution of the wire about the axis. A 
variation in the electromotive force is developed 
as the conductor or armature wire approaches and 
passes by the north pole of the field magnet, rang¬ 
ing from zero to a positive current maximum. 
The electromotive force then diminishes and 
ranges through a corresponding series of negative 
values while the armature wire approaches and 
passes by the negative pole. This complete set 
of values is called a “ cycle ”, including, as it does, 
the full range of positive and negative values; the 
duration of a cycle is termed a “period”; and 
the number of cycles per second is the “ fre¬ 
quency.” 

This will appear in the diagram (Figure 34), 
where the curve indicates the successive values of 
the electromotive force in the rotating coil as it 
cuts the lines of force, first in one direction and 
then in the other, time being measured along the 
horizontal line OX, and the curve shown corre¬ 
sponding to one complete revolution. The electro¬ 
motive force and current rise from zero to a max¬ 
imum at a, then fall to a minimum or zero at b, 
and pass through a corresponding variation with 
the current flowing in the opposite direction, 
reaching a corresponding maximum at c. The 
electromotive force developed will depend, as we 
have seen in our consideration of the direct-cur¬ 
rent dynamo, upon the length of the conductor cut- 


GENERATORS AND MOTORS 


87 


ting the field and the strength of the field. The 
first is, of course, determined by the number of 
turns to the loop ; the second, by the rate at which 
the rotating coil cuts the lines of force. It must be 
realized that only a part of a turn is “ active ” 
and capable of cutting the flux. 





Fig. 34: Curves showing successive values of the electromotive force of 
different kinds of alternating current. The letters a, a', and a" represent 
maximum positive values of electromotive force; c, c', and c" represent mini¬ 
mum values. Time is measured along the horizontal line OX, where b, b', and 
b" represent an electromotive force of zero. 

Single-phase Current. Such a current as we 
have illustrated is known as “ single-phase.” If, in 
addition to the single rotating loop illustrated, we 
employ one or more similar loops, connected to 
separate or extra collector rings but arranged at 








88 


EVERYDAY ELECTRICITY 


some definite interval with respect to the first loop 
or coil, we may secure a considerable variation of 
the current delivered. This variation admits of 
specially useful applications. 

Two-phase Current. For example, let us first 
consider a second conductor or loop, so arranged 
for revolution with regard to the first that it is 90 
degrees distant, but revolving with the first in the 
same cycle. A current will be generated in this 
wire no less than in the first, but the electromo¬ 
tive force produced at any given instant naturally 
will not have the same value as that in the first; 
and if we plotted these values in a curve, the sec¬ 
ond would be found to be just a quarter of a period 
behind the first, as shown in the diagram (Figure 
34). The current that passes out through the 
collector or slip rings, is what is known as “ two- 
phase ” current, it being developed by two dis¬ 
tinct sets of windings. Current of more than one 
phase is referred to as polyphase; and although it 
is produced by a single generator, yet essentially it 
involves two or more alternators, electrically dis¬ 
tinct yet working on the same mechanical system. 

Three-phase Current. If we arranged on our 
armature three loops or conductors spaced equally 
apart, connected at one extremity to one slip ring 
(such a fourth ring is not necessary and is seldom 
used) and at the other separately to three different 
slip rings, there would result current delivered in the 
form shown in Figure 34, which would be called 


GENERATORS AND MOTORS 


89 


“three-phase” current. Practically all transmis¬ 
sion lines now are three-phase, as the transmission 
of power by three-phase current is more economical 
of copper in the line conductors than by either sin¬ 
gle-phase or two-phase current. 

The Simple Alternator. In the alternator, as in 
the direct-current generator, we naturally increase 
the number of pole 
pieces from the two 
that have served in our 
explanations and dia¬ 
grams. The increase 
is made in order to ob¬ 
tain a rapid succession 
of oscillations, or high 
frequency, without re¬ 
quiring too swift a 
speed of rotation. But 
it should be remem¬ 
bered that a complete Fia. 35: A Multipolar Alternator with 

. 1 a Rotating Armature. 

cycle would correspond 

to the passage of the loop referred to, or of any 
given group of armature wires, across two ad¬ 
joining field poles, a north pole and a south pole, 
so that there are f cycles in one revolution, 
p indicating the number of poles. 

In a regular alternator, several conductors are 
used, and they are placed in the periphery of a 
rotating mass of laminated iron. Just as the num¬ 
ber of poles was increased, so the number of con- 







90 


EVERYDAY ELECTRICITY 


ductors or loops was also increased; and these 
conductors were placed in slots in the mass of 
laminated iron, the whole forming the armature. 
Laminated construction is used, as in the arma¬ 
ture of the direct-current generator, in order to 
prevent the development of eddy or Foucault cur¬ 
rents, which would reduce the flux and cause extra 
losses in the iron. The wires from the coils or 
loops go to the appropriate collecting rings. 

Field. Naturally, the field magnets cannot be 
energized, as in the direct-current dynamo, by 
the current generated flowing, wholly or in part, 
through the coils. The rapidly oscillating cur¬ 
rents would not produce the constant field de¬ 
sired. Accordingly, it is necessary to have the 
field coils energized by direct current produced by 
an independent generator, perhaps mounted on 
the same shaft, perhaps driven by a belt. 

Revolving Field Type. In the simple alternat¬ 
ing-current generator we have considered, the arma¬ 
ture revolves and the field is stationary. Such 
alternators now are found only in small electric 
lighting stations; for with high voltages and fre¬ 
quencies, the construction of such a large piece of 
rotating mechanism would be most difficult. Ac¬ 
cordingly, for generators of, say, 100 kilowatts and 
greater capacity, the armature with its laminated- 
iron construction is made the stationary part, and 
the field coils are arranged to revolve, being con¬ 
nected directly to the prime mover. Consequently, 


GENERATORS AND MOTORS 


91 


the connections to the armature are merely fixed 
taps or wires, while the revolving field coil receives 
its current through slip rings. 

Inductor-alternator or Synchronous Alternator. 
The inductor-alternator, which finds special ap¬ 
plication for generating high-voltage currents 
used in radiotelegraphy, although it has a con¬ 
stant magnetic field and armature, nevertheless 
has both of these elements stationary; and for the 
revolving part employs a so-called inductor, con¬ 
sisting of a laminated-iron core with polar projec¬ 
tions or a well-balanced disc of steel with teeth 
or grooves in its edge. The field coils and arma¬ 
ture windings are on the same frame, but on dif¬ 
ferent projections or pole pieces. The field coils 
are connected in series; there being an alternat¬ 
ing north and south pole, with an armature piece 
between. As the inductor revolves, the magnetic 
lines of force are cut alternately into and out of the 
armature windings, and thus electromotive force 
is induced in the armature. The inductor-alter¬ 
nator may be either single phase or polyphase, but 
it requires a separate exciter or source of current 
for the field coils. 

Frequency. Alternating-current practice in the 
United States has been standardized on a basis of 
a frequency of 25 cycles per second for power cir¬ 
cuits, and 60 cycles per second for lighting serv¬ 
ice, as anything much less than this is likely to 
produce a flickering that is trying to the eye, al- 


92 


EVERYDAY ELECTRICITY 


though there are some circuits in which 40 cycles 
are employed. 

Turbogenerator. The turbogenerator, or direct 
connected combination of a steam turbine with a 
generator, is to-day the usual arrangement and 
such units are now designed for large output. 
Consequently, with these large machines it is neces¬ 
sary from the mechanical standpoint to consider 
the speed of revolution and the weight of the 
revolving parts. The attempt is therefore made 
to have the revolving field as small and light as 
possible, but the construction must be of great 
strength to withstand revolving at high speed. 
Nickel steel is used for the core and the first 
windings are formed by straps of copper insulated 
but held in place by bars of phosphorus bronze. 
As regards its axis, the turbogenerator may be 
either vertical or horizontal, but the latter is now 
the more general practice. 

Alternating-current Motors. One of the great 
achievements of the development and application 
of the alternating current has been its availability 
for use with electric motors. The best of these 
alternating-current motors are more simple in 
construction than the direct-current motors and 
require less attention under severe conditions of 
service. On the other hand they have the disad¬ 
vantage of being unable to operate at as low speed 
and are not so easily regulated when the conditions 
of service vary as regards the demands of power 


GENERATORS AND MOTORS 


93 


and speed. Nevertheless, where a constant-speed 
machine can be used and alternating current is 
available, numerous devices known as induction 
motors may be employed and are eminently sat¬ 
isfactory and efficient. 

Alternating-current motors are divided into 
three main groups: (1) induction motors, which 
include the “ squirrel cage ”, and the phase-wound 
motor; (2) synchronous motors; and (3) com¬ 
mutator motors. 

Induction Motors. Perhaps the motor most 
commonly employed with alternating current is 
the so-called induction motor, which was invented 
by Nikola Tesla. This was at first polyphase, but 



Fig. 36: A simple diagram to show a rotating two-phase induction motor 
with rotating magnetic field. — One source of current is connected with the 
coils A and A '; the other alternating current, differing in phase by 90 , is con¬ 
nected with the coils B and B'. The direction of the magnetic field at any 
one moment is shown by the vertical and horizontal arrows, i he joint enect 
is to produce a nearly steady magnetic field, rotating in the direction shown. 
In this rotating magnetic field are placed closed coils of copper wire wound on 
a drum of laminated iron, forming the rotor, which will rotate under the action 
of the induced current in the coils, due to the revolving magnetic field. A 
pulley is fastened to the extremity of the axis of the rotor. 
























94 


EVERYDAY ELECTRICITY 


to-day induction motors are built either single¬ 
phase, two-phase, or three-phase. In this ma¬ 
chine, we have what is essentially a polyphase 
transformer with its secondary free to move. 
There is a reaction between the current and the 
magnetic field, and electrical energy transferred 
to the secondary is transformed into mechanical 
energy. In other words, we have a series of coils 
and windings; and as the magnetic field changes 
in a rotary direction, the coils in the rotor tend to 

follow the field. 

> 

“ Squirrel Cage ” Induction Motor. The lead¬ 
ing type of induction motor, known as the “ squir¬ 
rel cage ” induction motor, is a single or constant- 
speed machine, taking its name from the fact that 
its rotor is formed of heavy brass or bronze strips 
imbedded in the core parallel to the axis and con¬ 
nected at the ends to rings, the general effect re¬ 
sembling the wheel of a squirrel cage. 

Wound-rotor Motor. Instead of the short-cir¬ 
cuited rotor windings of the “ squirrel-cage ,s 
motor, the wound-rotor motor has coil windings 
that terminate in slip rings on the rotor shaft. 
Brushes are in contact with these slip rings, 
through which resistance can be introduced into 
the rotor circuit; and by changing this resistance 
by means of a drum control, the speed of the 
wound-rotor motor can be varied from full nor¬ 
mal speed to about half speed in any desired num¬ 
ber of steps, so that the motor can be brought up 


GENERATORS AND MOTORS 


95 


to full speed gradually without drawing more than 
full-load current from the line. This makes the 
wound-rotor motor particularly useful where 
speed variation must be maintained, as in a num¬ 
ber of industrial processes, and where high power 
is required for starting, as in very large machines. 

Synchronous Motors. The synchronous motor 
must run in step, or phase, with the alternator 
from which it receives its current; and some means 
of adjustment is required to bring the two into 
harmony. The synchronous motor, when com¬ 
pared with an induction motor, will show greater 
efficiency and a higher power factor, which also 
may be controlled. It must operate at a con¬ 
stant speed and requires an exciter for the field 
coils. It is not usually self-starting. 

Single-phase Series Motors. The single-phase 
series motor is used largely in railway work, where 
alternating current is furnished at high voltage, 
for the transformers can be carried on each motor 
car or locomotive. Possibly the most notable 
installation of single-phase series motors is that 
to be found in the electric locomotives on the 
New York, New Haven and Hartford Railroad 
between New York and New Haven. Alternating 
current at 11,000 volts at the trolley is trans¬ 
formed on each locomotive. These motors are 
designed to operate at from 250 to 300 volts al¬ 
ternating current, or 600 volts direct current, for 
which two motors are connected in series. 


CHAPTER IX 


Direct and Alternating Current 

The choice of current nowadays is largely de¬ 
termined by the special circumstances prevailing 
at the place of installation, involving also the con¬ 
ditions of generation and transmission of the cur¬ 
rent. Once the current reaches the point of util¬ 
ization, or where the work is to be done (as, for 
example, in lighting a building or operating one 
or more motors), one kind is likely to be as effec¬ 
tive as the other. On the other hand, when the 
current is being generated and transmitted to 
the point of utilization, and in the available 
means of utilization, there are important differ¬ 
ences. The advantages are in favor of the alter¬ 
nating current, so that some 95 per cent, of the 
electric energy generated and transmitted in the 
United States is of the alternating-current type. 

As the size of the conductor is restricted by con¬ 
siderations of expense, mechanical support, and 
so forth, it is apparent that more power can be 
passed economically if higher voltages are used in 
its transmission. Accordingly, it was found that 
by use of a transformer, current at the generator 
could be stepped up from a lower voltage for trans- 


DIRECT AND ALTERNATING CURRENT 97 


mission, a small current but at high tension pass¬ 
ing over the line, and then at the point of utiliza¬ 
tion correspondingly reduced to a larger current of 
lower voltage. With the desire to generate elec¬ 
tric energy as cheaply as possible at some water¬ 
fall or other point of economical production, there 
has finally developed the use of high voltages in 
order to operate transmission lines over as long 
distances as possible. 

The direct-current generator as it was first 
developed gave good service within a restricted 
area, but it was found, in New York, for example, 
after 1882, when incandescent lighting was first 
established, that it was necessary to have a num¬ 
ber of central stations in order to maintain the 
requisite voltage throughout the territory served; 
for, as we have seen, an incandescent light rapidly 
decreases in luminosity with a slight decline of 
voltage. This means larger feeders or conductors 
from generators to distribution points; with, of 
course, proportionately greater cost for copper and 
the development of isolated plants for buildings 
rather than of large central stations with their 
many economies. 

When it was found that alternating current, 
which was first used commercially for arc light¬ 
ing, could be generated and transmitted safely and 
efficiently, then the city lighting companies de¬ 
cided to remove boilers and engines from their 
local central stations, most of which constantly 


98 


EVERYDAY ELECTRICITY 


were receiving increased calls and required larger 
installations, and to install synchronous con¬ 
verters or motor generators. Alternating current 
received from one large central station at some 
convenient distance was used to generate direct 
current at 120 volts to serve the needs of the dis¬ 
trict. In this way, the advantages of both sys¬ 
tems were retained and a flexibility of service was 
secured. 

The same condition held with even greater force 
on electric railways of more than two or three 
miles in length. Here, on the trolley wires, the 
drop in voltage was very large; and this acted to 
limit the usefulness and distance of lines, until it 
was found that rotary converters could be in¬ 
stalled at a convenient point and alternating cur¬ 
rent at high voltage sent from a generating sta¬ 
tion. 

A serious disadvantage of the direct-current 
generator was that it did not lend itself to large 
capacities required for central stations as did the 
alternator form. The same was also true of the 
hydraulic turbine and hydroelectric stations, aside 
from the question of transmission. 

Transformer. The transformer mentioned above 
is a simple device with no moving parts. Around 
a closed core of iron are wound two separate coils 
of insulated wire, one of which is connected to 
a source of alternating electromotive force, the 
other being available for any desired use. 




Courtesy of the Westtnghouse Electric and Manufacturing Company. 
TRANSFORMERS 

Steel-Clad Transformer to Reduce the Voltage Large-Capacity Oil-Cooled Transformer, as Employed 

of a Transmission Line to That Required for the on Long-Distance Transmission Lines. Here windings 
Lighting and Power Circuits of the Consumer. and core are surrounded by circulating oil. 














DIRECT AND ALTERNATING CURRENT 99 


The coil connected with the source of alternat¬ 
ing current is called the primary, and the other is 
known as the secondary. Under the influence of 
the changing current in the primary, there will be 
a change of magnetic flux — that is, in the density 
of the lines of force — through the wire turns of 
both the primary and the secondary coils. If the 
number of turns in the primary coil is less than the 
number of turns in the secondary, then the voltage 
produced in the secondary circuit will be higher, and 
we shall have what is known as a step-up trans¬ 
former, which is used at the generating end in 
power-line transmission. If the number of turns 
in the secondary be less than in the primary, then 
we shall have what is known as a step-down trans¬ 
former, reducing the voltage from the transmission 
line to the distribution circuits; or where there is 
a high-voltage distribution circuit, reducing the 
voltage to the individual consumer by means of 
a small transformer. 

Synchronous Converter. After the transformer, 
probably the most important feature of a trans¬ 
mission system in many instances is the synchro¬ 
nous or rotary converter, which takes the alter¬ 
nating current and delivers it in the form of direct 
current at a convenient voltage — as, for example, 
550 volts for railway service, or 120 volts for light¬ 
ing. To-day, the converter is a very essential 
element of a large city lighting service, as it is in¬ 
stalled at a substation so that a district can be 



100 


EVERYDAY ELECTRICITY 


supplied with direct current without undue loss of 
potential and with economy in the generation and 
transmission. For example, in practically all the 
large cities there are extensive plants favorably 
located, usually at the waterside, where large 
turboalternators are installed to generate three- 
phase current at 60 cycles. This is transmitted 
to the different substations, there to be converted 
into direct current and distributed. 

The synchronous converter in its appearance is 
very similar to the direct-current multipolar gen¬ 
erator, but it is supplied with both collector rings 
and a commutator. To the former the alternat¬ 
ing-current leads are connected, and the machine 
runs as a synchronous motor; at the same time, 
direct current is obtained from the brushes on the 
commutator. In other words, in one machine 
with one set of windings there are contained both 
an alternating-current motor and a direct-current 
generator, so that the core loss and excitation loss 
are those of a single machine, not of two. Both 
motor and generator currents flow in the same 
winding. 


CHAPTER X 


The Telegraph 

The idea of using the electric current for trans¬ 
mitting signals appealed even as early as the 
eighteenth century, and various pith-ball devices, 
and later other electrical means, were devised for 
this purpose. All of this was, however, on a very 
small scale, and nothing positive could be accom¬ 
plished until the American scientist Joseph Henry 
made such improvements in the electromagnet as 
to render it adequate to exert mechanical power at 
a distance from the source of current. 

In 1831, around one of the upper rooms of the 
Albany (N. Y.) Academy, where he was a teacher 
of science, Henry arranged a wire more than a 
mile in length, through which he was able to make 
signals by sounding a bell. He also discovered 
that the electromagnet was applicable to the trans¬ 
mission of power at a distance, and from this dis¬ 
covery he developed a small magnetic engine. 
Henry also used the armature of an electromagnet, 
supplied with current from a battery through a 
long conductor, to close another circuit — what 
would be termed a local circuit; this being the 


102 


EVERYDAY ELECTRICITY 


germ of the modern telegraph relay. He devel¬ 
oped other similar experiments that were not con¬ 
sidered more than interesting laboratory matters 
until Professor Morse devised the electromagnetic 
telegraph. 

The Electric Bell. The simple electric bell has 
mounted in its frame a horseshoe electromagnet 



Fig. 37: A Simple Electric Bell and Its Circuit. 


whose coils are wound with wire. There is an 
armature of soft iron mounted on a spring and 
carrying the hammer or clapper of the bell. If it 
is desired that the bell should make simply a single 
stroke, the circuit is closed, permitting the cur¬ 
rent to flow through the coils; the armature is 
attracted; and the gong of the bell is struck. If, 
however, instead of making a single stroke, it is 
desired that the bell should vibrate, we have such 


























































THE TELEGRAPH 


103 


an arrangement as is illustrated in the diagram 
(Figure 37). One wire or conductor, connecting 
with the battery or other source of current, leads 
direct to the coil, and the other connects with the 
spring and through it to the magnet, where the 
other end of the coil is attached. When the cir¬ 
cuit is closed, the armature of the bell is attracted; 
but in passing toward the poles of the magnet, it 
breaks the circuit as indicated. Consequently, 
the spring forces the armature back, whereupon 



Fig. 38: Ordinary Household Bell Circuits. — (A) One bell and two push 
buttons. ( B ) Two bells and one push button. (&) Two bells and individual 
push buttons. 


the circuit is again closed and the same perform¬ 
ance is repeated so long as the circuit is kept 
closed. 

A bell circuit ordinarily is closed by means of a 
push button, as shown in the diagrams. Pressure 
on this device will cause the current from the bat¬ 
tery to flow through the coils of the magnet. 

Simple Bell Circuits. It is perfectly possible to 
have two push buttons, so that if either one (say, 
at the front door or the back door) is pushed, the 
bell will sound. Likewise, it is possible with one 
































104 


EVERYDAY ELECTRICITY 


push button to have two bells, so that bells in the 
basement, or on the top floor, or in the barn, will 
sound simultaneously. In fact, a number of bells 
and a number of push buttons can be included on 
a single circuit; and with a number of bells and 
push buttons, we can make our circuit as elaborate 
as we please. In place of a number of different 
bells, we can have an annunciator with one bell 
and separate magnet releases that will indicate at 
once the source of the signal; and this may range 
from a three-figure or four-figure affair, seen in a 
home or an apartment, to the large hotel board 
with several hundred drops. 

The Principle of the Telegraph. When Profes¬ 
sor Morse invented the electromagnetic telegraph, 
he devised the alphabet signal code of “ dots ” and 
“ dashes ”, known by his name, and, with slight 
modifications, universally used. Morse’s original 
arrangement of apparatus included the key and 
a recorder. In the recorder, the signals corre¬ 
sponding to the dots and dashes were marked on a 
paper strip by a point on one arm of a lever carry¬ 
ing the armature of the electromagnet. Once, 
this recording device was to be seen in telegraph 
offices, especially under conditions where it was 
necessary that the original record should be pre¬ 
served ; but ordinarily with the American teleg¬ 
rapher, as early as 1850, it became a custom to 
read the dots and dashes by the clicks of a special 
instrument rather than by the pierced tape. 


THE TELEGRAPH 


105 



There was developed what is known as a sounder, 
consisting of a horseshoe electromagnet whose two 
spools of wire are inclosed in a rubber or vulcanite 
cover, and whose poles attract an armature against 
the action of a spring, there being a sharp click on 
its downward journey, and also when it is released 
by the current and pulled up 
by the action of the spring. 

Unlike the armature of the 
vibrating electric bell, the 
armature of the sounder stays 
down as long as the circuit 

• i j l i . Fig. 39: A Telegraph Sounder. 

is closed and does not move 

up under the action of its spring until the circuit 
is opened. The agency for opening and closing 
this circuit is a device known as a key, consist¬ 
ing of two elements carefully insulated and con¬ 
nected by a lever, which, when depressed, will 
make contact between the two parts. With this, 

of course, there must be some 
form of constant battery. 
The usual arrangement was 
at first with what is called a 
bluestone cell of the gravity 
or Daniell type, later replaced by some form of 
storage or dry cell or by current from a generator. 

It will be noted that in addition to the main 
knob of the key, there is a small knob controlling 
a switch which enables the circuit to be opened or 
closed. This switch will always be closed except 



Fia. 40: A Telegraph Key. 














106 


EVERYDAY ELECTRICITY 


when the operator is sending a message; for then, 
by depressing the key, he is able to close the cir¬ 
cuit at will. A modern arrangement of the key is 
known as the vibroplex, or, as telegraphers term 
it, “ the bug.” The lever of this is constantly 
vibrating, and connection is made by a slight 
squeeze of two knobs. (Both types of key are 
shown in the accompanying plate.) This avoids 
the tendency to develop telegraphers’ paralysis. 
There is, of course, the same arrangement of key 
and sounder at the distant station; and we can 
have a single line with a number of stations, each 
of which has its sounder and key, but at which 
the operator will not answer unless he hears his 
own particular call letter sounded. It is perfectly 
feasible to have three, four, or more sets of instru¬ 
ments upon the same line, provided that the 
battery is strong enough to give an impulse ade¬ 
quate to overcome the resistance in the circuit, and 

furnish sufficient current at 
each one of the sounder mag¬ 
nets to attract the armature. 

The Relay. There is ob¬ 
viously a limit to the dis- 
Fiq. 41 : a simple Telegraphic tance over which a single 

battery or a group of bat¬ 
teries can act; and the electric impulses, when 
they reach a station, may be so very weak as not 
to operate the sounder, even though its windings 
and resistance have been increased in order to 






Courtesy of the Western Union Telegraph Company. 
THE TELEGRAPH 


(A) An Ordinary Telegraph Key (at the Left) and the Vibroplex. 

(B) Operator Sending a Message with the Vibroplex. 

( C ) Front View of Switchboard in the New York Office of the Western 
Union Telegraph Company, One of the Busiest Stations in the World. 





THE TELEGRAPH 


107 


make it more sensitive. Accordingly, under these 
conditions, what is known as a relay is employed, 
and so, too, is a local circuit. The relay is an 
electromagnet wound to higher resistance than is 
that of an ordinary sounder, with an armature so 
delicately mounted that it will respond to far more 
feeble currents than would affect the sounder. 
More than that, following out a principle discov¬ 
ered years ago by Joseph Henry, the relay, by the 


q .Sounder Sounder u 

— i Une i . i 



Fig. 42: A Simple Closed Circuit of the Electric Telegraph. 


movement of its armature, serves to make or break 
contact in a local circuit having a sounder and a 
battery. Or the relay may serve as a repeater to 
transmit the message over the next stage of its 
journey. These instruments are comparatively 
simple, and we see them arranged in connection 
with the switchboard, with a number of plugs by 
means of which the local lines can be directed to 
the circuits as required. 

Naturally, the telegraph operator requires con¬ 
siderable facility and speed in transmitting mes- 




















108 


EVERYDAY ELECTRICITY 


sages; and under many conditions, particularly 
those of intermittent service, and for branch-sta¬ 
tion work, he has maintained his preeminence 
over various mechanical automatic devices that 


oloea/Bautder 


o Local Bounder 


LocoASocs/rder i 


Latte 


"tfjflSJIIJi 

Inca/Battery 


Ke/ay 


ZBottvy 

Zaw-i- 

Baifey-±z- 



LjheBattery 

M'l'F 


.Key 

Circuittopen 
\tt>rsen ding 


6nwxf = ~ 1 


" Ground 

Fia. 43: A closed-circuit telegraph line, with a way station, showing 

local circuits and relays. 


have sought to displace him. These have, how¬ 
ever, in great part superseded him in the large 
central stations where much through business is 
handled, as between New York and Chicago. 


American Morse Code 

A - 

B — • 

C • 

D - • 

E • 

F - • 

G - - • 

H ... 

I 

J - - • 


International Code 

A - 

B - • . 

C - 

D - • 

E • 

F • • — • 
G - - • 

H ... 

I 

J- 



























THE TELEGRAPH 


109 


American Morse Code 

K - - 

L — 

M - - 
N - • 

O • • 

p • • * 

Q . . _ . 

R • • • 

5 • • • 

T - 

U • • - 

V 

w - - 

X - 

Y • • • • 

z 

6 . • • • 

1 • - - • 

2 ♦ • — • • 

3 • • 

4 • • • • — 

5 - 

6 . 

7 -- • 

8 — • 

9 - • - 

0 - 

Period • --- • 

Comma • - • - 
Interro¬ 
gation - • • - • 


International Code 

K - - 

L - • • 

M - - 
N - • 

O- 

P - - • 

Q-- 

R - 

S . . . 

T - 

U - 

V . . . _ 

w - - 

X - - 

Y - - - 

Z - - 

1 -- 

2 • -- 

3 • . . - - 

4 . . - 

5 . 

6 _ ... . 

7 -* • • 

8 -- • 

9-- 

0 - 

Period. 

Comma 
Interro¬ 
gation * --• • 












110 


EVERYDAY ELECTRICITY 


The Morse Code. The Morse Code is an elab¬ 
orate system of signals corresponding to individual 
letters, digits, and punctuation marks. It can be 
interpreted either by the ear or in visible char¬ 
acters. In this system, dots, dashes, and spaces 
are used. To make a dot, the operator quickly 
depresses his key, and immediately releases it, so 
that an impulse of current of slight duration passes 
over the line. To make a dash, the key is de¬ 
pressed, but a longer interval intervenes before 
it is released. A space is a short interval between 
two consecutive dots. It follows the release of a 
key and does not occur in any letter composed of 
dashes. 

The use of the space, which is confined to Amer¬ 
ican Morse working, is made clear by the follow¬ 
ing illustration. To make the letter A, repre¬ 
sented by a dot and a dash (as will appear from 
the accompanying representation of the code), 
the key is depressed, immediately released, at 
once depressed again, and this time kept down for 
a slight interval before release. To make the 
letter I, which is represented by two dots, the key 
is depressed, immediately released, at once de¬ 
pressed again, and again immediately released. 
To make the letter O, two dots are sent, as in the 
case of the letter I; but they are separated by an 
appreciable interval or pause. The dash in its 
duration is equivalent to two dots (or units), as 
is also the letter space; and the ordinary space is 


THE TELEGRAPH 


111 


equal to the dot. The space between words is 
equivalent to three dots; and the sentence space 
to five dots. 

The American Morse and the so-called Inter¬ 
national (Continental) code are given in the ac¬ 
companying tabulation, the latter employing no 
space and showing a few variations from the Amer¬ 
ican practice. The International code is used 
exclusively for submarine cables, for radio com¬ 
munication, and for land lines in countries outside 
of the United States. 

Current Supply. The energy required for work¬ 
ing a telegraph circuit was at first supplied from 
bluestone or gravity cells, and these were ar¬ 
ranged in series, with as many as 25 to 350 for 
long-line batteries. These cells now are found at 
only small, isolated stations, having elsewhere 
been supplanted by the storage battery. The 
storage battery could be arranged so as to supply 
current to a switchboard at any desired voltage by 
tapping off at various points in the battery cir¬ 
cuits ; so that from 80 to 320 volts, for example, 
could be taken from the switchboard and distrib¬ 
uted to any desired circuit, the circuits being all 
arranged in parallel. The dynamo now is used 
generally at the large stations in place of either 
primary or secondary batteries, and a spare (or 
reversal) installation is maintained in case of 
breakdown. When a dynamo is used, it is usual 
to employ four or five generators in a set, with the 


112 


EVERYDAY ELECTRICITY 


armatures arranged in series; a quite common 
arrangement being for each of the generators to 
give either about 70 volts or some other convenient 
arrangement of voltage for the circuits in use. 
Two sets of generators are kept, so as to develop 
different polarity. 

The Repeater. In our consideration of the relay, 
we have already suggested the necessity of using 
a sensitive electromagnetic receiving device to 
open and close the next section of the line, in 
the same fashion as is done for the local circuit. 
This is the special function of an instrument 
known as the automatic repeater, which is so 
arranged that it acts to repeat messages in either 
direction. 

Duplex Telegraphy. It was early apparent that 
because of the large cost of constructing a tele¬ 
graph line, some system would be welcome whereby 
two messages could be sent over the line in differ¬ 
ent directions at one time; in other words, that a 
single wire so arranged that over it at one station 
one operator could receive, while another could 
transmit, would be a very useful contrivance. 
For duplex working, it is possible to use either the 
differential method or the bridge method. 

In the first method, use is made of the differ¬ 
ential relay, in which the battery current divides 
between two equal wires, passing around the core 
of the relay in opposite directions, so that the 
relay is not magnetized when the key at the home 


THE TELEGRAPH 


113 


station is closed. A special set of resistance coils 
and condenser is employed to reproduce the elec¬ 
tric conditions of the line as regards resistance and 
capacity. When it is desired to send a signal 
from one station to the other, the key at the home 
station is depressed, and the impulse transmitted 
thus operates the relay at the distant station as 
its balance of current is distributed. Likewise, 
if the corresponding key at the distant station 
were opened or closed, the relay at the home sta¬ 
tion would be similarly affected. 

In addition to the differential relay, there is 
also employed a polarized relay, which responds to 
changes in the direction of the current instead of 
to changes in current strength, and which can be 
reversed at will by the sending operators. When 
polar and differential relays are combined, two 
operators at the same time and with the same cur¬ 
rent can send two messages over the same wire 
and in the same direction. 

In the bridge duplex system, which is used in 
England and in cable working, there are four 
resistances, corresponding to the arms of the well- 
known Wheatstone bridge that figures in electrical 
measurements. 

Duplex telegraphy once assured, the next 
achievement was to develop the transmission of 
four messages over one line, two in each direction. 
As in the case of the duplex, the quadruplex cir¬ 
cuits can be of either the differential or the bridge 


114 


EVERYDAY ELECTRICITY 


type. They require neutral and polarized relays 
in combined series. 

Automatic Telegraphy. Under modern indus¬ 
trial conditions, anything that will speed up an 
operation in telegraphic transmission increases 
the capacity of the line and naturally is of con¬ 
siderable advantage. In what is known as the 
Wheatstone automatic device, a tape punched 
with the appropriate signals is fed into the auto¬ 
matic transmitter. Obviously, the tape can be 
punched by a less skilled operator, as all that is 
necessary is to depress either the dot key or the 
dash key, and make the appropriate perforation. 
Naturally, a number of operators can work at this 
task of perforation of messages; and the tape, 
when perforated, can be fed into an automatic 
transmitter whose unusual feature is the pole¬ 
changing switch. 

At the receiving end, there is a polarized relay 
whose armature vibrates only in correspondence 
with the signals. By means.of an inking wheel 
connected with the armature, the message devel¬ 
oped on the basis of the current reverses is in¬ 
scribed on a tape from which it is later decoded; 
this work also being distributed among as many 
operators as are necessary. 

Multiplex Telegraphy. Various systems of mul¬ 
tiplex telegraphy, whereby four or more messages 
in each direction can be handled, have been devel¬ 
oped and are used commercially in the United 




Receiving Operators at the Western Union Telegraph Company’s Main 

Office in New York City. 


Sending and Receiving Apparatus of the Multiplex System, as Used by 
the Western Union Telegraph Company. 


THE TELEGRAPH 

















THE TELEGRAPH 


115 


States. In fact, for its business between cities 
the Western Union company has developed a 
highly efficient multiplex system, which includes 
not only automatic transmission but also the 
printing of the messages on the appropriate blanks 
ready for delivery. This system of course in¬ 
creases the capacity of a single line eightfold; and 
it is so arranged that not only can messages be 
received in printed form but a tape can be per¬ 
forated for retransmission. 

This system makes use of the principle of the 
distributed use of the line, with synchronous dis¬ 
tributors at either end — that is, revolving switches 
moving at the same velocity around discs, con¬ 
trolled by tuning forks so that they are in abso¬ 
lute synchronism. In this system, each operator 
or transmitting machine has the use of the line 
for a fraction of a revolution around the disc, 
which is shared with other operators or transmit¬ 
ting instruments. The discs are divided into 
insulated groups of segments, each group being 
connected to one of the signaling and receiving 
machines. A rotating contact brush is connected 
with the line wire and passes over the discs so that 
it makes a connection between the line and the 
individual circuits or channels. At the distant 
station, a rotating contact brush operates in per¬ 
fect unison as to position and time, so that the sig¬ 
nal sent through a particular segment is received 
at the corresponding segment. 


116 


EVERYDAY ELECTRICITY 


This arrangement is operated by means of a 
perforated tape upon which the operator impresses 
the appropriate characters — not in the ordinary 
Morse but in a special five-unit code that is more 
economical in the use of the line. There are 31 
different code signals — 26 corresponding to the 
letters of the alphabet, the other five being (a) for 
the return of the carriage on the distant printer, 
(6) for the line feed of paper on this machine, and 
for ( c ) letter shift, ( d ) figure shift, (< e) space. The 
signals are received and transmitted to individual 
printers which operate, in connection with the 



• • • • • •••••• •• •• • ••• • • • • • ••• • •• ••• • 

• •• •• • * •• ••• • ••• • • •••••••• • • • • • ••• •• 

• • • • • • •• •••••• • •• • • • • •• • •• •• •• 



Fig. 44: Punched tape for the automatic transmitter in the multiplex 
telegraph system. See also Fig. 49. 


necessary relays and resistances, with a warning 
bell, calling the attention of the receiving operator 
to the necessity for shifting the paper or similar 
work. 

When this system is worked quadruplex-duplex, 
as is the case between such cities as New York and 
Chicago, it is possible to carry over 45 words per 
channel, or from each of the four transmitters at 
either end; giving a total of 360 words per minute 
for the line. This apparatus requires not an ex¬ 
pert telegrapher but merely one skilled in prepar¬ 
ing the perforations. The work is done at a key¬ 
board similar to that of an ordinary typewriter. 





THE TELEGRAPH 


117 


The multiplex-system tape is here shown in com¬ 
parison with the tape over an ordinary cable trans¬ 
mitter, which uses the International (Continental 
Morse) code (Figures 44 and 49). It will be noted 
that in the multiplex-system tape the perforations 
run crosswise. 

Printing Telegraphs. It would seem almost an 
anachronism that after so many years a large 
amount of the telegram business of the world is 
handled in special signals and code instead of 
direct print. Direct-printing mechanisms, how¬ 
ever, in addition to their use in such systems as 
the multiplex, find employment also in the familiar 
stock-ticker telegraph and news-bulletin service, 
in which a number of instruments connected in 
series transfer the received signals into type char¬ 
acters on tape or on a sheet. The usual form of 
arrangement consists of a master transmitter lo¬ 
cated at, or in close proximity to, the stock ex¬ 
change or other primary market; or at the source 
of the news or quotation service. The impulses 
of alternating current that cause the rotation of 
the type wheel are so rapid as not to affect the 
sluggish printing magnet; yet when the type 
wheel comes to rest, the printing-magnet is 
brought into play. There may be only one line 
wire; but on the other hand some ticker systems 
have two line wires and two type wheels each; one 
of the wheels to carry the letters, and the other to 
carry the figures. 


118 


EVERYDAY ELECTRICITY 







Submarine Telegraphy. As soon as the land 

telegraph had been estab¬ 
lished, possibilities of com¬ 
munication by means of a 
conductor laid on the bed of 
a river or ocean appealed to 
many interested in this work. 
As early as 1851, at the sug¬ 
gestion of a colliery engineer, 
the gutta-percha-covered 
copper wire was armored or 
protected by winding it first 
with hemp and then with 
strands of iron or steel wire; 
and this general type has 
remained in use and is the 
accepted form even to-day. 

In the submarine cable, 
the problem involved a con¬ 
ductor not only of great 
length and small cross sec¬ 
tion with a naturally high re¬ 
sistance, but also possessing 
other properties due to the 
effects of its electrostatic 

Fig. 45: Cross Sections of a conductive Pflnnpitv TllP 
Modern Ocean Cable. — (A) LUlluuulve CdpdClby. Alie 

S^ P eSr p t°,ioUWa^ cable acts as a condenser 
SSrSfffSrAiSSffi possessing a certain electro- 

land coast; and (2?) shore end • , .1 , .. 

as used on the Irish coast, Static Capacity, SO that it 
armored with steel strands to , 1 . . i 1 . • „ 

protect the cable from injury. taKes considerable time tor 



THE TELEGRAPH 


119 


the current to charge it and then for the cable 
again to be discharged. This time factor of course 
limits the speed of signaling; for if the separate 
signals are sent too quickly, they become confused 
and unintelligible. 

In the early days, Lord Kelvin, the famous elec¬ 
trician, realized that the conditions of operation 



Fia. 46: Diagram showing the principle of the siphon recorder. 


meant not the use of high-voltage currents but 
rather the use of a more sensitive detecting device; 
and consequently he invented the mirror galvanom¬ 
eter, which, by means of a beam of light and a 
reflecting mirror, was able to respond to very slight 
currents flowing in the coils of the galvanometer. 

This was used until Lord Kelvin devised the 
siphon recorder, which was really a sensitive gal- 























120 


EVERYDAY ELECTRICITY 


variometer but with a suspended coil in the gap 
between the poles of a strong permanent steel 
magnet. To this rectangular coil of fine, silk- 
covered copper wire through which the current 

HERBERT T WADE 

--y—VAn/ vuv - 


NEWYO RK CITY 

Fia. 47: Tape record from the syphon recorder of a submarine cable, 
with the decoded rendering given immediately above. 

passes, is attached a very fine glass tube, one end 
of which dips into a vessel containing ink, and the 
other end of which rests on a strip of paper moved 
by clockwork. 



4 

On a submarine cable, the method is to indicate 
a dot by current impulses sent in one direction and 
a dash by current transmitted in the opposite 
direction; the needle of the galvanometer being 
caused to vibrate from one side to the other, de- 


















THE TELEGRAPH 


121 


pending upon the direction of the current. Be¬ 
tween the signals, the cable is grounded to dis¬ 
charge the conductor, so that it is clear for the en¬ 
suing impulses. In the simple cable, therefore, 
instead of a single key, the usual arrangement is 
with a double or pole-changing key; so that by 
depressing one or the other of the keys, the ap¬ 
propriate signal will be sent. The signals are 
arranged in Morse code, the Continental or In¬ 
ternational Morse system being employed. 



Fig. 49. Punched tape for the automatic transmitter of a submarine cable. 
Positive and negative impulses are imparted to the line by contacts made 
through the upper and lower rows of punched holes. See also Fig. 44. 

In place of the hand key, it is very customary to 
use automatic transmission. A tape is first me¬ 
chanically punched by an operator and then fed 
into a transmitter where the appropriate connec¬ 
tions are made through the perforations by means 
of copper brushes. This tape has a center row of 
perforations to guide it through the machine, and 
above and below are the holes that are punched. 
Automatic transmission is possible only where the 
cables have rather heavy cores, and it brings the 
speed of transmission up to about fifty words per 
minute, or to the speed limit of the cable. 

Duplex Working. It was early realized that a 
submarine cable represented a considerable in- 




122 


EVERYDAY ELECTRICITY 


vestment, yet was susceptible of carrying but 
limited traffic. Therefore, in 1870, there was 
devised by Muirhead and Taylor a method for 
duplexing so as to provide for sending messages in 
both directions. This method involved an artifi¬ 
cial cable in which the electrical resistance and the 
electrical capacity were realized by means of re¬ 
sistance coils and condensers. This arrangement 



Fig. 50: Diagram of a bridge duplex system for submarine-cable signalling. 

will appear in the diagram (Figure 50), which in¬ 
dicates that the outgoing current will be divided 
between the real and the artificial cable. The 
terminals of the receiving instrument have the 
same potential, and are not affected. Rut any 
incoming current will pass through the siphon 
recorder coils and will go into the earth through 
the artificial cable, a signal being recorded in the 
usual fashion. 

After duplex working was realized, the next 
problem was to secure satisfactory cable relays 
that would take the message from one line at an 





























THE TELEGRAPH 


123 


intermediate land point, say Halifax, Guam, or 
Honolulu, and automatically transfer it to the 
next line. These cable relays are made more 
sensitive than the siphon recorder, so that a speed 
of transmission rising up to three hundred words 
per minute has been attained with one type of 
relay across the Atlantic Ocean. 

The heavier the copper core or conductor of the 
submarine cable, the more rapid the rate of sig¬ 
naling. This core is formed of stranded copper 
wires and is surrounded by several layers of gutta¬ 
percha insulation. The insulation is in turn pro¬ 
tected by a thick layer of jute, and outside of this 
comes the armoring of galvanized steel wires. The 
deep-sea portion of the cable requires the least 
protection ; but as soon as the shore is approached, 
heavier armoring is required and the steel strands 
are made heavier to resist the action of rocks and 
other agencies. 

A cable requires the most careful workmanship, 
and it must be tested frequently during its con¬ 
struction, to make sure that the conductivity and 
insulation are as required. When it is ready for 
shipment, it is transported to special cable ships 
and there stowed in tanks from which it can be 
paid out as the ship sails the carefully charted 
course. In the case of parting of a submarine 
cable, one of these cable ships will cruise to and 
fro about the point where the break is known to 
have occurred and will pick up and raise the ends 


124 


EVERYDAY ELECTRICITY 


and splice them together by inserting a connect¬ 
ing piece. By means of the instruments, it is 
quite possible to measure the resistance of the 
broken length of cable; and this known, the en¬ 
gineer can determine quite accurately the situa¬ 
tion of the break, so that the cable steamer has 
little difficulty in locating it. In 1922, there were 
seventeen cables across the Atlantic Ocean. Not¬ 
withstanding the cheaper radio installations for 
trans-Atlantic communication, submarine cables 
continue to be used on account of their secrecy. 

The Fire-alarm Telegraph. One of the earliest 
applications of the telegraph in the United States 



Warm Sox 
with notched wheei 
Circuit interrupter 
Humber of Box 43/ 

Fig. 51: A simple fire-alarm-box circuit, with notched wheel, and relay and 
bell at the distant station. Note that the circuit will be interrupted by the 
slots on the wheel, so that there will be 4-3-1 interruptions or impulses, indicat¬ 
ing by corresponding strokes of the bell that an alarm has been turned in at 
Box 431. 

was to the transmission of signals giving alarm of 
fire. Gradually, apparatus of considerable effi¬ 
ciency was developed, so that now larger cities and 























THE TELEGRAPH 


125 


even many of the important towns are provided 
with a network of circuits over which any citizen 
can turn in an alarm of fire, to be received at 
fire headquarters or other central station, whence 
an alarm is in turn sent out to the appropriate 
fire-fighting agencies. Usually, the fire-alarm tele¬ 
graph consists of the box to which the citizen 
has access, where, by pulling a hook or turning 
a handle, a clockwork-like mechanism is set in 
operation. The first feature of this mechanism 
is a disc at whose periphery are teeth or notches 
that make and break the circuit in accordance 
with some prearranged code. 

These circuits go to a relay at headquarters, 
and there operate secondary circuits that may be 
as complex as desired. In a simple town installa¬ 
tion, for example, the relay circuit would operate 
an alarm bell, and also gongs at the various fire 
stations, without any intermediate agency. In 
other headquarters, the relay might operate 
merely an annunciator giving the number of the 
box from which the signal was sent; and the 
alarm to the apparatus houses and pumping 
stations might be sent out from still another 
circuit, either by hand or by means of an appro¬ 
priate toothed wheel placed on a transmitting 
mechanism. 


CHAPTER XI 


The Telephone 

Every day in the United States over sixty mil¬ 
lion telephone calls are made — of which four 
million are handled in the city of New York alone 
— at a rate of one hundred thousand calls a min¬ 
ute in busy hours. We know that the instrument 
is to be found in almost every house throughout 
the United States, over thirteen million having 
been in use in 1920, or twelve telephones to every 
hundred persons; that by it we can converse 
readily with any one, not only in our own neigh¬ 
borhood, but even across the continent. 

The Fundamentals of the Telephone. Examin¬ 
ing the apparatus that is carefully inclosed in the 
casings and box, we first find the receiver — the 
device that half a century ago represented about all 
there was of the telephone. In the first standard 
telephone, there was a bar magnet around one of 
whose poles was wound a coil of fine, silk-covered 
copper wire. In front of this pole was a thin 
diaphragm of iron, close to the end of the magnet 
but not in contact. This diaphragm was, in fact, 
so thin that it recalled the 44 tintype ” on which the 
photographer at the seashore resort used to place 


THE TELEPHONE 


127 


our pictures, and it was arranged so that it could 
vibrate under the stimulus of the sound waves. 
For we know that sound is only a series of rapid 
motions set up in the air by some vibrating me¬ 
dium ; that a high sound represents a very rapid 
vibration, and a lower one represents a vibration 
that is less rapid. The nature and quality of the 
vibrations, of course, determine human speech and 
the communication of ideas. 


A 

Co// 


B 

Co// 



Soft 

/ron 

Ojx 


Fig. 52: Original Telephone Circuit of Alexander Graham Bell. 

If we look at our diagram, it will appear that if 
the soft-iron diaphragm vibrates under the influ¬ 
ence of the voice, and approaches, and recedes 
from, the pole of the magnet, it will vary the field 
of force that cuts the coil of fine wire and will give 
rise to currents of electricity that will alternate in 
harmony with its own vibration. Such being the 
case, if we take the terminals of this coil and con¬ 
nect them with a similar arrangement by means of 
a wire or a wire-and-ground circuit, then it will 
appear that the currents flowing in the distant 
coil B will correspond to those generated at A , 
and that the iron diaphragm there will be corre- 


























ns 


EVERYDAY ELECTRICITY 


spondingly attracted and repelled. Such a rapid 
movement of the diaphragm will naturally give 
rise to corresponding vibrations in the air, which 
the ear perceives as sound. This device remains 
an essential element of every telephone installa¬ 
tion, in the form of the receiver. True, to-day a 
modern receiver has two coils and a bipolar magnet 


//iopbrapnr ferrotype Iren, 
Japanma to 
Prevent /fast 


> Case and Cap of/lardRubber 

Welded Mapnet 





ConcealedB/'ndinp fbste 

, fb/e fieces ofA/ob Crude Afopnefic/ro/i 
Wound Coils \ Welded lo Magnet 

(/?&novcbl$) dross Cup, Air end dust 7/jbf 

Fiq. 53: Cross section of a standard receiver of the American Telephone 

and Telegraph Company. 


made of various pieces, but in all its essentials it 
is the original telephone. 

Naturally, at first, the telephone currents were 
very weak and it was found that introducing a 
battery into the circuit improved matters, as the 
amount of current modified or varied by the vi¬ 
brations was correspondingly greater. Then it 
was realized that though the telephone would re¬ 
spond to variations in the current, yet it was 
possible to maintain conversation over only short 
distances, until use was made of some form of 












THE TELEPHONE 


129 


microphone transmitter in which under vibration 
the resistance of a substance would vary. Quite a 
few such were tried until experience demonstrated 


MamisAee/ Muslin iVosher 


/nsu/ofinj? 
Mica Disc' 


/t/aminum Diap/rroym 
Heavy D/own Brass /vcef/ofe 


CenfraiDamping 



wg/r Efficiency 
Carbon Button 

. 'ffigiHGa/va/iized 
Dice/ Bridge 


One Piece Drown Brass fie/f 

Fia. 64: Cross section of the standard transmitter of the American 
Telephone and Telegraph Company. 


that if the diaphragm of the transmitter were 
placed against one of two discs of carbon between 
which were granules of the same substance, the 



Fia. 55: A local telephone circuit, with induction coil. 


resistance of an electric circuit of which this was 
a part would vary proportionately to the vibra¬ 
tions. This, of course, meant that there must 


































130 


EVERYDAY ELECTRICITY 


be a battery to supply the current; and then 
it was found that if in the transmitter circuit 
there was included a transformer or induction 
coil, or rather its primary, then by means of 



a bridging magneto set. 

the secondary the current sent out over the wire 
would be stepped up or raised in potential, so that 
it would act over far greater distances. 

A form of signaling apparatus to call the dis¬ 
tant party was next developed in the shape of a 








































THE TELEPHONE 


131 


small magneto generating an alternating current 
of from 60 to 80 volts, which would energize a bell 
or buzzer at the distant station and make the de¬ 
sired calling signal. The line ordinarily was ar¬ 
ranged for sending these signals, not the more 
rapid vibrations due to the telephone currents; 
and in fact, the user of the telephone had to cut the 
signaling arrangement out of the circuit, on ac¬ 
count of the high resistance of the magneto, and 
connect the telephone to the line. This he does 
to-day automatically by removing the receiver 
from the hook ; this essential feature of the modern 
instrument having originally figured as early as 
1878. 

Switchboards. If the simple telephone were 
confined to but two stations its usefulness would 
be seriously restricted; and very early in its his¬ 
tory — 1877, in fact — it was realized that there 
was required a central point where an operator 
could receive the signal of a calling subscriber, 
find the number of the person with whom he 
desired to talk, and complete the connection. 
Instead of a group of magneto call bells, each ring¬ 
ing, there was but one bell; and what was called a 
drop or indicator, operated by the calling current, 
was connected with each subscriber’s line. 

The Early Switchboard. Each line had an an¬ 
swering jack or terminal, into which could be in¬ 
serted a plug connecting with the exchange opera¬ 
tor’s instrument, so that the operator could ascer- 


132 


EVERYDAY ELECTRICITY 


tain the connection desired and, by means of a 
connecting plug and cord, make the connection 
when the subscriber would ring his magneto. The 
line would then be open for conversation. There 
were also listening and ringing keys; so that on 
each subscriber’s circuit the operator could con¬ 
nect her apparatus, communicate with the calling 
subscriber, and ascertain the number or connec¬ 
tion desired, and could transmit the appropriate 
alternating current to ring the subscriber’s bell 
when a call was made. 

Common-battery System. The elimination of 
the hand-operated magneto for the calling signal 


Induction 

Coil 



Switch Hook 


Fig. 57: A Common Battery Substation Circuit. 

between subscribers and the central station, was 
one of the most important accomplishments in 
the development of American telephone practice. 
Furthermore, with the taking away of the mag¬ 
neto, there was eliminated also the battery that 
was required by the subscriber’s instrument, and 
in its place all the energy needed at each station 
was derived from the common battery, a large 
storage battery, at the central station. 















THE TELEPHONE 


133 


This common-battery system, first introduced 
in 1896, is now generally used in the larger cities 
and towns and in the important new installations, 
and involves a substantial economy in initial 
equipment, as the calling magneto was perhaps the 
most expensive feature of the older installation, 
and the local batteries required periodic attention 
and renewal. Where introduced, the common- 
battery system saved four seconds on every call, 
in addition to other advantages to the subscriber. 

Party Lines. The first lines for which more than 
two instruments were employed were arranged in 
series, and this required bells or ringers, the coils 
of each of which had so many turns (with the re¬ 
sulting impedance) that difficulty arose because 
of obstruction to the telephone currents. In 1889, 
the so-called bridging bell was invented; and it 
was this invention that made possible the party 
line which has done so much for the farmer, and 
to improve rural conditions. Originally, each 
subscriber had his own individual code signal, 
with a certain number of long and short rings; 
but later, various schemes of selective ringing 
were adopted, so that the operator at the central 
station now can call any one of a group on the 
party line without the signal being heard by the 
others. Up to four subscribers on a single line, 
excellent service is given. 

Development of the Switchboard. The problem 
of the switchboard at the central station or ex- 


134 


EVERYDAY ELECTRICITY 


change early became very important, and has con¬ 
tinued as one of the controlling features in the 
development and use of the telephone. In the 
first place, the number of subscribers and the size 
of the board became too large for a single operator 
to make all the desired connections. Then two 
or more boards were placed side by side, across 
which the operators could reach with their flexible 
cords. Very soon the limiting distance of such 
operations also was exceeded, and the next step 
was to divide the board into sections and to join 
the respective sections by metal strips or wires, so 
that one operator could connect with another op¬ 
erator by means of the strips and ask her to make 
the connection with a subscriber sought who was 
in her section. In other words, there resulted 
what later were called “ trunk lines ” between 
switchboards, and what was known as a “ trans¬ 
fer board ” was developed, which proved unsatis¬ 
factory, both for ordinary work and, still more, 
for the increased service that early showed the 
board’s limitations. 

Multiple Switchboard. The answer that the 
telephone engineers gave to this problem, was the 
“ series multiple ” switchboard. Here every op¬ 
erator by means of a spring jack had access to 
each subscriber’s line entering the exchange, with¬ 
out any necessity for “ trunking ” the calls. This 
arrangement is very costly and elaborate and com¬ 
plicated, but at the outset it saved ten seconds on 


THE TELEPHONE 


135 


every call, and it soon proved its value. In this 
system, each subscriber’s line, after entering the 
exchange, is multiplied so that one set of conduc¬ 
tors can be carried to the appropriate spring jack 
at each board. One side of the circuit goes 
through the board to the ring or outer contact of 
the jack, and the other goes to the cut-off spring 
contact of the jack, the object of which is to cut 
off the line-signal circuit during conversation. 
As will appear from Figure 59, each subscriber’s 
line was connected with the answering jack and 
with its appropriate line signal, which was duly 
energized, indicating to the operator the number 
of the person calling. As soon as this signal was 
observed, the operator could insert her plug (con¬ 
nected to her own earpiece receiver and circuit) 
in the appropriate answering jack and receive the 
number desired from the calling subscriber. 

The “ Busy ” Signal. Each line was connected to 
a number of sections of the board so that an opera¬ 
tor had access to the jack of any subscriber, and 
the obvious situation developed in which a circuit 
might be in use when an attempt was made to 
establish a connection. Under these conditions 
and to prevent confusion, there was early estab¬ 
lished the “ click busy test ”, so that, once a plug 
was inserted in any jack, at the rings of all of the 
other jacks of that same subscriber an electrical 
potential was placed, by means of which any opera¬ 
tor, before completing a connection, would know 


136 


EVERYDAY ELECTRICITY 


at once that the line was busy. This was done by 
the operator’s placing the tip of the connection 
plug against the ring of the jack into which it was 
to be inserted to make the desired connection. 
The ring was touched momentarily before the 
complete insertion was made; and if the line 
sought was already in use, a sharp click would be 
heard by the operator in her head telephone, due 
to the high potential automatically placed on 
this special group of jacks through a connection 
established elsewhere on the switchboard. 

Improving the Switchboard. The series mul¬ 
tiple switchboard met the difficulties in many 



Fig. 58: Switchboard Plug and Jack. — Sectional view showing connec¬ 
tions when the plug is inserted in the jack. S = sleeve of plug; T = tip of 
plug; R — ring of plug; S' = sleeve of jack; T' = tip of jack; R' = ring 
of jack. The jack-sleeve connection cannot be shown in full. It is continued* 
from A, behind the plug, and connects on to the plug sleeve. To make a “busy” 
test, the operator touches the tip of the plug against the sleeve of the jack, 
before inserting the plug in the jack. 

ways and was the basis for further improvements, 
one of which was the branch terminal and mul¬ 
tiple board, where the line and the line signals 
were connected to the jacks and the jack springs 
in such a way as to prevent false operation and the 
actual disconnecting of the line signals from the 
circuit when the line was in use. At this time, 
provision was made for the automatic restoring of 
the drop of the annunciator to its original position 









































THE TELEPHONE 


137 


when a plug was inserted in the answering jack of 
the calling line; this doing away with the neces¬ 
sity for the operator’s restoring the drop signals 
by hand. 

The multiple switchboard was developed long 
before the common-battery method came into 
existence; and when this radical innovation was 
adopted, the switchboard underwent considerable 
remodeling. No longer were there line and dis¬ 
connect signals at the board, as there were sub¬ 
stituted tiny electric lights covering all the relays 
on each subscriber’s circuit. This method has 
now become standard, and is used for all larger 
manually operated boards. 

Operations at the Switchboard. The user of 
the telephone little appreciates what happens at 
the distant switchboard. Although, as may be 
inferred, the apparatus itself is complex, the proc¬ 
ess is so well organized that the sequence of opera¬ 
tions follows quickly and regularly. When the 
receiver is removed from the hook, a circuit is com¬ 
pleted ; and by means of a relay, a small incandes¬ 
cent lamp, associated with the answering jack, is 
lighted. The operator, on noting that the light is 
energized, takes up a cord and inserts the plug in 
the jack appropriate to the subscriber’s line. This 
cuts the light circuit out; and then the opera¬ 
tor, after throwing her listening key in, answers 
the subscriber by saying, “ Number, please ”, and 
receives from him his order, the subscriber first 


138 


EVERYDAY ELECTRICITY 


mentioning the exchange. The operator then 
calls the distant office and gives the number to the 
“ B ” operator, who assigns to her a trunk line. 



Fig. 59 : Simplified Diagram of a Modern Common-battery System. 
Description of Operation: When subscriber A removes his receiver from 
the hook, current flows through the circuit from battery B *, operating 
line relay C and closing the circuit through line lamp D. The lighting of D 
in front of the operator notifies her that the subscriber desires to make a call, 
and she inserts plug E in jack F. This completes the sleeve circuit through G 
and operates cut-off relay H, opening the circuit through C and putting out D. 
At the same time, the talking circuit (indicated by heavy lines) is completed, 
and supervisory relay I is operated, shunting supervisory lamp J before it has 
time to light. The operator then connects subscriber A with the desired person 
by means of the other side of the cord circuit, first making a “busy” test to 
determine whether or not the line is in use. K shows the operator’s set in posi¬ 
tion to be connected for the “busy” test. For the sake of clearness, the ring¬ 
ing keys usually employed to call the subscriber are omitted from the diagram. 
When A has finished his conversation, he restores his receiver to the hook, open¬ 
ing the talking circuit and releasing the armature of 7, which removes the shunt 
around supervisory lamp J. J lights and notifies the operator that A has com¬ 
pleted his conversation. 

This she connects with the calling subscriber by 
plugging in with the other cord of the pair, one 

* The several batteries marked B are actually one common 
storage battery. 





















































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THE TELEPHONE 


139 


cord of which she had previously used in answer- 
ing. The two operators, with their respective 
sections of the switchboard, are shown in the 
accompanying plate. 

At the distant office, the incoming operator has 
located the desired subscriber’s number on the 
multiple switchboard before her. After first test¬ 
ing the line to see whether it is busy, she inserts 
into the multiple jack the plug of the connecting 
trunk line connected with the exchange of the 
calling subscriber, and automatically the ringing 
is started. If she finds the line busy, she does not 
insert the trunk line into the calling subscriber’s 
jack but plugs into a jack that sends back the 
“ busy ” signal, so that as much effort is involved 
in returning the busy signal as in completing the 
connection, if not more. 

Toll Switchboard and Toll Lines. The toll 
switchboard is one of the features of the central 
exchange, as it deals with the lines going out into 
a more extensive territory than the immediate 
district covered by that special exchange and the 
allied group. Accordingly, here the outside trunk 
lines center, and the operator must make the con¬ 
nections and arrange for the correct recording of 
the individual calls. 

The Machine Switching System. The increas¬ 
ing number of subscribers and the huge switch¬ 
boards already described, naturally require the 
services of a vast number of operators, and the 


140 


EVERYDAY ELECTRICITY 


amount of manual labor at each of the telephone 
exchanges is very large. Hence, machine-switch¬ 
ing systems, aiming to do away with the operator, 
have been developed. 

The Telephone Dial. In the system used in the 
larger American cities, there is a modification of 
the standard equipment, but this does not involve 



Fig. 60: Diagram showing the progress of a call from an automatic subscriber 
to another automatic subscriber, or to a manual subscriber. 


any change in the usual form of subscriber’s in¬ 
strument and call bell, except that the instrument 
is provided with a calling device, known as a 
“ dial ”, which is mounted on the base of the tele¬ 
phone set. In this dial are ten finger holes bear¬ 
ing, respectively, the numerals one to nine, and 
also zero and the word “ operator ” in the tenth 
hole. In the installations in the larger cities, 
each finger hole save two (those for one and zero) 







































































THE TELEPHONE 


141 


has three letters of the alphabet, so that the dial 
carries the complete alphabet with the exception 
of the two letters Q and Z. In this equipment, the 
subscriber, by rotating the disc, can place the dif¬ 
ferent letters and numbers successively at the 
index and thus indicate his call to the central 
exchange, where the connection is duly made 
without the agency of an operator. The dial in¬ 
strument is shown at A in the accompanying 
plate (facing page 142). 

The Selector Frame. There is at each central 
office a so-called “ line-finder frame ”; and when 
the receiver is removed from the switch hook by 
the subscriber, before he dials his call, his line is 
selected by a finder and connected to a dial 
“ sender ” by means of a “ sender selector.” This 
operation is practically instantaneous, and when 
it is completed, if the line is available, the sub¬ 
scriber will hear a so-called “ dial tone.” The 
next stage of the operation is the transmission of 
the electrical impulses on the decimal basis to the 
so-called “ sender ” at the central station. This 
is an electrical mechanical device whose operation 
depends upon the impulses that the subscriber 
causes by making and breaking the circuit with 
his dial disc, which has successive stops, corre¬ 
sponding to the numbers on the dial. This sender 
receives and registers these impulses and in turn 
translates them to the proper control apparatus, 
which is not operated on the decimal system. 


142 


EVERYDAY ELECTRICITY 


Distributing the Calls. The first function of 
the “ sender ”, which is permanently associated 
with the “ line finder ” originally used, is to start 
up and select a trunk connection to the office de¬ 
sired — in the case of our diagram, the Pennsyl¬ 
vania exchange in New Y 7 ork. This can be done 
either directly or through an office selector, in case 
there are more trunk groups than can be placed 
on the district selector. Now, if the Pennsyl¬ 
vania exchange also is on an automatic basis, the 
trunk connection chosen has as its terminal an 
“ incoming selector ” frame and the original sender 
will now cause the call to be repeated through the 
incoming selector to a final selector and thence to 
the particular line desired. After the connection 
is thus completed, the calling subscriber will be 
informed by audible signals whether the station is 
being rung or whether the line is busy; and if the 
line is out of order, the connection will be auto¬ 
matically completed to an operator who will so 
inform the calling subscriber. 

In short, what happens in the mechanical sys¬ 
tem is that the “sender” so operates the mecha¬ 
nism at the “incoming selector” as to locate the 
group of trunks leading to the “ final selector ”, 
in which are grouped practically five hundred 
lines in which the desired call is located and where 
the connection is made. The “ final selector ” 
first operates to test the line to determine whether 
it is busy; and if the line is clear, the connection 




' g 

Company. 


C 

Courtesy of the American Telephone and Telegraph 


MODERN TELEPHONE EQUIPMENT 

(A) American Telephone and Telegraph Company’s Standard Dial 
Instrument. 

( B) Vacuum-Bulb Repeater in Its Socket. 

(C) General View of a Machine-Switching Installation. 































THE TELEPHONE 


143 


is established and the called person’s bell is auto¬ 
matically started ringing. If the line is busy, the 
selector will not establish the connection and the 
calling subscriber will receive a “ busy ” signal. 

If two subscribers at the same exchange, or at 
two exchanges, both fitted with the mechanical 
system, are involved, it is quite possible to ex¬ 
change regular calls without any outside inter¬ 
ference. There are, however, other calls, such as 
toll and long-distance calls, and calls designated 
for changed numbers, which may require the as¬ 
sistance of the operator in the main switching 
office. Therefore, at each mechanical board, 
special facilities are provided for this class of serv¬ 
ice, and operators are maintained who will also 
take care of subscribers requiring assistance for 
other reasons. A general view of a machine¬ 
switching installation is given at C in the accom¬ 
panying plate. 

Telephone Lines. The first conductors used for 
the telephone, and for the ordinary telegraph wires, 
were of galvanized iron, which gave satisfactory 
service for the telegraph. It was soon found, 
however, in connection with the telephone and the 
rapid oscillation of its currents, feeble in their 
strength, that very minute currents were devel¬ 
oped, which, though unnoticed in the telegraph, had 
serious effects on the transmission of speech, giv¬ 
ing rise to “ cross talk ” and troubles due to induc¬ 
tion. Furthermore, the currents on adjoining 


144 


EVERYDAY ELECTRICITY 


telegraph wires were also heard on the telephone 
circuits. It was realized that telephone engineers 
had a large problem on their hands, which became 
more complicated as developments followed in 
telegraphy through the use of high-frequency cur¬ 
rent and increased speeds of transmission. 

Finally J. J. Carty, chief engineer of the Ameri¬ 
can Bell Telephone Company, made the experi¬ 
ment with a metallic circuit, using a return wire 
instead of the ground. In experiments conducted 
between Boston and Providence, extraordinary 
success was secured. 

Metallic Circuits. These first metallic circuits 
were of iron wire. Although they were a great 
improvement, still “ cross talk ” continued; and 
it was not until the development of hard-drawn 
copper wire for the all-metallic circuit that marked 
progress was gained. In 1884, two hard-drawn 
copper wires 0.104 inch in diameter were placed 
on poles between New Y T ork and Boston, making 
long-distance conversation possible; and in 1892, 
New York and Chicago were connected for a 
thousand-mile conversation in similar fashion. 

The decision to do away with grounded circuits 
was a most radical step, for it involved the re¬ 
building of the plant, not merely along the line 
but at central stations. Nevertheless, it was well 
worth the effort; and now copper conductors 
are generally employed, especially on all long cir¬ 
cuits. 


THE TELEPHONE 


145 


Telephone Cables. At one time, practically all 
electrical conductors were placed on poles, not 
only in the country but in large cities; and as the 
requirements of electric service increased, these 
pole lines not only were unsightly but furnished 
many hazards, due to the crossing of high-tension 
lines with ordinary conductors. Accordingly in 
some of the larger cities (notably New York, in 
1882), by legislative acts wires were ordered under¬ 
ground at a time when the growth of telephone 
selvice demanded a large number of conductors. 
These circumstances led to the development of 
compact cables that could be placed underground 
or supported on poles more readily than could a 
number of single wires. At this time, however, 
desirable though they were, cables were not suited 
for telephony, and they acted to cut down the 
transmission of the voice currents to such an ex¬ 
tent that a mile of cable could cause as much effect 
on these currents as a hundred miles of overhead 
lines. 

At first, the cables used for telephone transmis¬ 
sion had insulation of rubber or gutta-percha, but 
these substances seemed unsatisfactory. Then 
it was found that if cotton were introduced into 
the cables instead of rubber, and the cable covered 
with a lead pipe, a high degree of insulation could 
be secured. 

The next improvement of the cable was to re¬ 
place the cotton by paper, so that the paper cables 


146 


EVERYDAY ELECTRICITY 


soon came into service and formed the basis of 
many subsequent improvements. From local 
cables, long-distance cables were developed; and 
although at first their use was restricted, never¬ 
theless, with the loading coil elsewhere described, 
they were found to be adapted to general service. 
In fact, telephone conversation now can be carried 
on over a cable a thousand miles in length more 
readily than in 1882 over a cable of a mile or even 
less length. To-day, cables are made with 2,400 
wires in a single lead sheath, an amount of com¬ 
pactness found essential in such a city as New 
York, where congested buildings and narrow 
streets afford but limited underground space for 
electrical conductors. 

Loading Coils. The current produced by the 
voice in a telephone circuit consists of a series of 
very rapid oscillations, ranging from 400 to 2,000 
cycles per second; and as such, it is subject to the 
various conditions common to alternating cur¬ 
rents in general. However, in this field of high 
frequency and small amplitude, any weakening 
of these currents beyond a certain point is likely 
to lead to distortion, which is troublesome in the 
extreme. 

As a result of his studies of alternating currents 
and the resonance of electric waves, Professor 
Michael I. Pupin of Columbia University devised a 
system of so-called “loading coils”, which could be 
introduced into the circuit to counteract and reduce 


THE TELEPHONE 


147 


this attenuation. These loading coils possessed 
an inductance and a capacity that were specially 
adapted to the circuit; and the result was that 
they so strengthened the transmission of the elec¬ 
trical waves that a much greater amount of energy 
reached its destination. These coils did not bring 



Fig. 61 : Diagram showing Pupin loading coils connected in the line circuit. 

to the circuit any additional energy; they simply 
served to make the line a better conductor for the 
telephone currents. 

These coils first were introduced in various 
underground cables in and about New York, and 
later were employed on an underground cable 
leading to Philadelphia; this marking the begin¬ 
ning of an extensive use of the device, which is 
now found on the lines from Boston to Washing¬ 
ton, and over long-distance lines generally. In 
fact, a type of cable with loaded coils has been 
developed so that Boston to Chicago can be con¬ 
nected in this manner and clear conversation 
maintained. 

Nature of the Coils. These coils are constructed 
of wire wound over cores of iron wire, and are 
placed at predetermined intervals in the circuit. 
The calculation of the winding and of the amount 
of wire used was a very delicate matter, which had 











148 


EVERYDAY ELECTRICITY 


to be verified by experiment, as did also the de¬ 
termination of the intervals at which the coils 
should be located. On open lines, they are usually 
placed about eight miles apart; on cable circuits, 
however, the interval is usually between one and 
two miles. This comparatively simple arrange¬ 
ment at once doubles the range of open-line trans¬ 
mission and increases the range of cable transmis¬ 
sion at least three or four times. 

Repeating Amplifiers. It was early realized 
that with increasing distance, the current flowing 
over a telephone line was so weakened by trans¬ 
mission that finally a point was reached where not 
enough energy was transmitted to operate the 
receiver. 

The first telephonic repeaters were electro¬ 
mechanical ; and although they served to amplify 
the current for its next stage, yet at the same time 
they introduced distortion, which had its effect in 
the quality of the sound. To-day, the successful 
vacuum-tube repeating amplifier that is generally 
employed, and is used on such circuits as those 
between New York and San Francisco, is based on 
the wireless-telegraph detector known as the grid 
audion and patented by Doctor Lee de Forest in 
1908. 

The de Forest repeating amplifier consists of an 
exhausted bulb of glass somewhat similar to an 
ordinary incandescent lamp; but in addition to 
the filament, the bulb contains a plate and a grid. 


THE TELEPHONE 


149 


This repeating amplifier acts as an electric valve, 
with the weaker current so controlling a greater 
that, with the circuits arranged as in the diagram 
(Figure 62), a weak current from a distant trans¬ 
mitting station will deliver back into the telephone 
line stronger currents — exact reproductions of the 
original enfeebled controlling currents, but with 
many times their energy. One of these repeaters 
is shown at B in the plate facing page 142. 



Fig. 62 : Simplified diagram of a vacuum-tube repeater circuit. For the 
sake of clearness, the plate and grid at the left-hand side of the filament are 
omitted. 


A Long-distance Circuit. These repeating am¬ 
plifiers not only increase the limits of long-dis¬ 
tance conversation but also make it possible to 
employ small-gauge wires along the line, increase 
the economy of underground and pole cables, and 
render such installations possible where once only 
open-wire construction was available. Not only 
is less cable cost involved for the line installation, 
but increased continuity of service is also obtained. 




















150 


EVERYDAY ELECTRICITY 


For example, an underground cable route is main¬ 
tained from Boston to Washington by way of 
Providence, Hartford, New Haven, New York, 
Philadelphia, and Baltimore. For these circuits, 
telephone repeaters are located in cities along the 
route, but at Princeton, New Jersey, and at Elk- 
ton, Maryland, special buildings have been erected 
for housing the equipment. 

The operation of this cable route may be appre¬ 
ciated from the fact that the total length of under¬ 
ground cable from Boston to Washington is about 
455 miles, and one of the circuits carried by this 
system of loading conductors consists of Number 
10 B. & S. standard gauge from Boston to New 
York, Number 13 gauge from New York to Phila¬ 
delphia, and Number 10 gauge from Philadelphia 
to Washington. This circuit as thus arranged is 
equivalent to about 30 miles of Number 19 gauge 
standard cable; and this, by means of repeaters 
located at Hartford and Philadelphia, is reduced 
to approximately 11.5 miles. 

Long-distance Telephony. Long-distance tele¬ 
phone connection began to increase its limits as 
soon as satisfactory apparatus and conditions of 
operation were secured. Thus the New York-to- 
Boston line was made possible by the all-metallic 
circuit to New York; the New York-to-Denver 
line by the use of the loading coil; and the New 
York-to-San Francisco line by the use of the re¬ 
peater or amplifier. 


THE TELEPHONE 


151 


Telephone service between the Atlantic and 
Pacific coasts is handled over a group of four wires, 
the arrangement consisting of two “ side circuits ” 



Fig. 63 : Diagram showing a phantom circuit in a long-distance line, whereby 
three speaking circuits are obtained with two sets of conductors. 

and one phantom circuit. As a result, three si¬ 
multaneous transcontinental connections may be 
established; and the four wires also can be ar¬ 
ranged to carry four telegraph circuits, over which 


Otflpot Tr »u fqm i er Output fron i fo r mcr 



Fig. 64: Diagram of a vacuum-tube repeater circuit employing two repeater 
elements, each line being balanced against an artificial line. 

may be transmitted eight simultaneous messages. 
This is done by the addition of “ composite appa¬ 
ratus” to the main telephone circuits. This trans¬ 
continental telephone line is 3,400 miles in length, 








































































152 


EVERYDAY ELECTRICITY 


and is formed of Number 8 B. W. G. copper wire, 
0.165 inch in diameter and weighing 870 pounds 
per circuit mile. 

Carrier Multiplex Telephony and Telegraphy. 
The latest development of combined telephony 
and telegraphy has been evolved in the United 
States and is known as “ carrier-current multiplex 
telephony and telegraphy.” This involves the 
transmitting of several voices simultaneously over 
a circuit, and, at the distant station, the separa¬ 
tion of these voice currents after they have passed 
together over the same wires. In other words, 
the problem here presented and solved consists of 
setting up electrical voice waves from independent 
sources in such a manner that they can be sepa¬ 
rated and diverted to individual receivers. The 
method employed is quite complex, but essentially 
involves the use of a combination of currents, one 
of which is a current produced by the vibration of 
the voice, whereas the other is a high-frequency 
current employed as a “ carrier ” of a voice cur¬ 
rent. These two currents are combined into one 
current that preserves the essential characteris¬ 
tics of both. In this form of telephony, a number 
of these actual currents (as many as four), each of 
a different high frequency and each with a sepa¬ 
rate voice current impressed upon it, can be sent 
out over a single pair of wires, in addition to the 
ordinary voice current employed. 

At the receiving end of the line, electrical filters 


THE TELEPHONE 


153 


are connected to the main circuit, each filter being 
designed to pick out the current of a particular 
frequency and that only; and in this way the 
various carrier currents are diverted to their sepa¬ 
rate and special circuits. Furthermore, over the 
usual pair of conductors, even when arranged for 
these carrier currents, a circuit can be arranged 
so that twenty-four simultaneous telegraph mes¬ 
sages can be sent. 

The new carrier-current system is designed for 
long-distance lines, as the apparatus is expensive 
and complex. When more widely installed, how¬ 
ever, it will bring about substantial economies in 
service, since it will permit much more extensive 
use of the single pair of conductors. 


CHAPTER XII 


Electric Lighting 

The first widespread and general use of electric¬ 
ity, outside of the telegraph, was to furnish illumi¬ 
nation, and in no field have more conspicuous 
triumphs been scored. To-day, the electric light 
is possible on an isolated farm in the country or at 
a camp in the woods. It can be rapidly installed 
.in almost any location, and it has raised the stand¬ 
ard of living and convenience in an immeasurable 
degree. 

The possibilities of electricity in this direction 
long were anticipated. After Volta discovered his 
pile, other scientists noted the heating properties 
of the current and the spark that resulted upon 
making and breaking the circuit, so that from the 
incandescence of a heated wire or from a constant 
spark it was thought possible to find a means of 
securing artificial light. 

In 1800 , Sir Humphry Davy used charcoal at 
the spark points; and later, as more powerful 
batteries were placed at his disposal, he developed 
the electric arc, finally securing a spark that passed 
over a space equal to four inches and brought the 
charcoal to white heat. He found further that 


ELECTRIC LIGHTING 


155 


the carbons must be brought into contact and then 
slightly separated, before the spark would pass. 
Davy placed his electrodes in a horizontal posi¬ 
tion, so that the heated air caused the luminous 
flow of electricity to bend upward; and accord¬ 
ingly, he named the bowed flame “ arc.” 

Rods of charcoal were used for electrodes until, 
in 1843, Foucault introduced electrodes of car¬ 
bon made from the coke from gas furnaces, and 
these were utilized in the electric 
lights of the day; especially in such 
a one as was first employed for 
lighting in Paris in 1848, which de¬ 
rived its current from a large voltaic 
battery. But the arc light as an 
illuminant was of little avail so long 
as the battery was the one source 
of electricity; for even of the power- 
ful Grove type, some forty to sixty bon electrodeB - 
cells would be required, and such a battery would 
not last more than two or three hours. 

About 1870, the Gramme dynamo became avail¬ 
able to furnish current for arc lamps as well as for 
other purposes. In 1876, Paul Jablochkov (1847- 
1894) invented an electric “ candle ”, consisting of 
two rods of carbon separated by an insulating 
medium, a spark being produced at the upper ex¬ 
tremity of the rods. So far as the United States 
was concerned, however, it was not until 1877, 
when Charles F. Brush invented his arc lamp and 




















156 


EVERYDAY ELECTRICITY 


dynamo, that the lighting industry really could 
be said to have had its origin. 

A direct-current dynamo operated the lamps in 
series, the voltage across each arc was about 50 
volts, and the circuits ranged up to the capacity 
of the individual generators. For street illumina¬ 
tion, the arc lamp at once found favor. Soon, in 
the United States, 250,000 open arc lamps were 
installed for street lighting or for the illumination 
of public buildings or large shops, and a great in¬ 
dustry sprang up, with central stations to provide 
the current. The open arc lamp used by Brush 
required about 500 watts and had a maximum in¬ 
tensity of about 1,200 candles at an angle of about 
45 degrees. 

The mechanism of the open arc lamp provided 
for the automatic approach of the carbons as they 
were consumed at the arc, with due regard for the 
fact that the positive carbon was worn away more 
rapidly than the lower. Such a mechanical ad¬ 
justment is required in all arc lamps unless hand 
feeding is employed. The luminous crater at the 
center of the positive carbon is the principal source 
of light. The chief drawback to the arc lamp was 
that although it afforded a bright spot of intense 
illumination beneath the lamp, this illumination 
did not extend to any considerable distance. Nev¬ 
ertheless, in spite of this, and in spite of the fur¬ 
ther fact that the carbons burned away rapidly 
and required frequent replacement (or “ trim- 


ELECTRIC LIGHTING 


157 


ming ”, as it was termed), the early arc lamp was 
useful and was widely employed. 

With direct current, a minimum electromotive 
force of from 40 to 50 volts was required for each 
arc; for alternating current, which became in¬ 
creasingly used, 30 to 35 volts sufficed. The first 
lamps were arranged in series and high-tension 
currents were used, but a later arrangement was 
to have the lamps in parallel, or two in series 
across the current mains. 

The Inclosed Arc. In 1893, Jandus improved 
on the open arc by bringing out an arc lamp 
in which the space where the arc was formed was 
inclosed; so that soon after the arc began to oper¬ 
ate, the oxygen was exhausted and an atmosphere 
remained consisting very largely of nitrogen. 
L. B. Marks showed that under these conditions a 
small current and a voltage of from 80 to 85 volts, 
in place of the 50 volts of the open arc, would 
operate economically. Furthermore, the carbons 
would not be consumed so rapidly, lasting for one 
hundred hours or more instead of possibly for one 
tenth of that time in the open arc. The inclosed 
arc was less efficient as a source of light, but it 
was far more economical and became widely em¬ 
ployed. 

The Flame Arc. The next development in arc 
lighting was the flame arc, devised in 1898 by 
Bremer. Fluorides of calcium, barium, and stron¬ 
tium, in the form of salts, were introduced into the 


158 


EVERYDAY ELECTRICITY 


carbons and gave to the flame of the arc a range of 
colors by varying the chemicals on the basis of 
their spectra. When these materials were heated, 
it was possible to obtain a considerable range of 
color and increased efficiency of illumination. In 
fact, a light very close to daylight, with a blue- 
white arc, was developed for use in chemical and 
photographic processes. 

The next development was the so-called “ lu¬ 
minous arc ”, which had a negative lower elec¬ 
trode consisting of an iron tube packed chiefly 
with magnetite (iron oxide) and titanium oxide in 
the approximate proportion of 3 to 1. The mag¬ 
netite is a conductor that is easily vaporized, and 
the result was a large arc flame to which the tita¬ 
nium imparted a high brilliance. The positive 
electrode was a short, thick, solid cylinder of cop¬ 
per that was consumed very slowly. This lamp 
was known as the magnetite arc, and, on account 
of its higher intensity, was valuable in still pho¬ 
tography, in motion-picture studios, in motion- 
picture projection, and in certain fields of stage 
lighting. 

Uses of Arc Lights. The arc in all its forms was 
forced to give way to the high-power incandescent 
lamps, which, as will soon appear, were later devel¬ 
oped and were useful for outdoor and other illu¬ 
mination. To-day the most important uses of the 
arc are for searchlights employed on vessels of 
war and in coast defense, and in the motion-pic- 


ELECTRIC LIGHTING 


159 


ture industry. In the searchlight that is now 
made so that we can pick up an airplane at a 
distance of about 15,000 feet, or a battleship at 
40,000 to 50,000 feet, the flame arc is employed, 
and special carbons have been developed for this 
purpose. On coast defenses a 60-inch reflector is 
used; 36-inch and 24-inch mobile units are sup¬ 
plied for use in the field. Likewise, in the motion- 
picture industry, efficient arc lights have been 
produced, and particularly with such methods of 
feeding as insure a uniform arc that keeps centered 
in the projection apparatus. 

Various attempts have been made to produce 
an arc between two surfaces of mercury; and the 
most successful arrangement — in fact, the only 
one that achieved commercial success, was that 
devised by P. Cooper Hewitt. With the Hewitt 
light, in an exhausted bulb of glass or quartz, an 
arc is established between two surfaces of mercury, 
or between an anode of iron and a cathode of mer¬ 
cury. As light, however, this arc is deficient, not 
having all of the spectrum colors and being lacking 
particularly in the red rays, so that the visible 
spectrum consists chiefly of violet, blue, green, and 
yellow rays. The light emitted has, therefore, a 
greenish color, which is not attractive in that it 
gives to a living person a peculiar pallor. The 
mercury arc emits virtually no red rays at all, and 
attempts have been made to supply this defi¬ 
ciency, but without success. For certain purposes, 


160 


EVERYDAY ELECTRICITY 


in photo-engraving establishments, photographic 
studios, drafting rooms, and open spaces, it has 
been used with advantage. Inclosed in quartz 
tubes, it finds application for sterilizing water, for 
medical purposes, and for photography, as it is 
rich in the ultra-violet rays that are especially 
serviceable in these fields. 

Incandescent Electric Lamps. Appreciating the 
property of the electric current to heat metals to 
the point of incandescence when the current is 
sufficiently strong and the wire used is small, a 
number of inventors sought, between 1841 and 
1848, by the use of Grove and Bunsen voltaic 
cells, to employ as sources of light certain metals 
heated by the electric current. Nothing was done 
of a practical nature, however, until the dynamo 
was invented and generally available. In 1877, 
Thomas A. Edison began his notable experiments 
in this field, using platinum, but this he found 
volatile and, with its low melting point (3,200° F.), 
unsuitable for the purpose. Realizing that car¬ 
bon possessed a very high melting point, Edison 
decided to use it as a luminous resistance; but he 
experienced difficulty in obtaining a filament suf¬ 
ficiently small and permanent. 

In 1879, Edison carbonized a strip of paper, 
which he sealed in an exhausted glass vessel or 
bulb ; using platinum wires for leading in the cur¬ 
rent, because this metal had the same expansion 
as glass, and therefore neither the vacuum nor the 


ELECTRIC LIGHTING 


161 


strength of the bulb was affected by leaking due 
to temperature changes. Platinum leads were 
used for incandescent lamps for practically thirty 
years and were perhaps the most expensive ele¬ 
ment in their cost during this time. Fortunately, 
with the diminishing supply of this metal, a sub¬ 
stitute was found by using two metals together 
whose combined expansion was the same as that 
of platinum and glass. 

In 1882 , central-station distribution of current 
was begun in New York City, and a few months 
previously in London. The current was furnished 
by a direct-current generator at a potential of 
about 116 volts. This seemed satisfactory both 
for the generation of the current and for its con¬ 
sumption in the lamp, but soon it was found that 
the range of distribution was somewhat limited. 
As more distant customers were obtained, it was 
necessary to establish new central stations to 
meet their requirements, as well as to keep up the 
potential on the line; for the luminous efficiency of 
a carbon filament increases with its temperature, 
and the temperature of course depends upon the 
current flow. 

The incandescent lamp has developed in size 
and efficiency until to-day for ordinary purposes 
it has supplanted the arc lamp, even for outdoor 
illumination, and the higher-efficiency, gas-filled 
incandescent lamps are now employed for street 
lights. With the development of the incandes- 


162 


EVERYDAY ELECTRICITY 


cent lamp has come reduced cost of operation; 
and thus have been brought to a great majority 
of American homes greater convenience and econ¬ 
omy combined with better illumination. 

Definitions. To measure the emission of 
light or the radiant power of a luminous source 
based upon its capacity to produce the sensation 
of light, there is employed as a unit the “ lumen ”, 
which is the amount of light emitted by a point 
source of one-candle power in a unit solid angle, 
or steradian — that is, the angular space sub¬ 
tended at the center of a sphere by that portion of 
its surface equal to its radius squared. The 
“ candle power ”, the unit of luminous intensity, 
no longer is derived from the actual paraffin 
candle, as once was the case, but is based upon a 
standard source of light maintained at the lead¬ 
ing national physical laboratories of the world. 
The unit of illumination is the foot candle, which 
is equal to one lumen per square foot. 

Types of Incandescent Lamps. In ordinary use, 
there may be encountered four kinds of incan¬ 
descent electric lamps: the ordinary carbon; 
that with the metallized filament, known as the 
“ Gem ” ; the tantalum ; and the tungsten. The 
last-named, which usually bears the trade name 
“ Mazda ”, has supplanted the others on account 
of its increased efficiency and better illumination. 

From 1885 to 1906, a remarkable increase took 
place in the use of electric light, and a correspond- 


ELECTRIC LIGHTING 


163 


ing decrease in its cost. In this period, the cost 
of current decreased from twenty cents to eleven 
cents per kilowatt hour, and the price of the 16- 
candle-power carbon lamp decreased from a dol¬ 
lar to twenty cents. The efficiency of the lamp 
was in the meantime improved from 5 watts per 
candle (2.51 lumens per watt) to 3.1 watts per 
candle (4.05 lumens per watt). In other words. 



■ * — • 20 Cand/e power 

Carbon Gem Tungsten 

Fig. 66: A comparison of the amounts of light given by different incandes¬ 
cent lamps. Each lamp shown consumes 50 watts, and the arrows show 
proportionally the intensity of the candle power in different directions in the 
different lamps 

y" 

for the same amount of energy the consumer was 
getting more illumination and was paying less 
for it. 

The Gem Lamp. In 1906, came the first real 
important development in the carbon-filament 
lamp, which consisted of carbonizing the filament 
at much higher temperatures. In this way, a wire 
with an increased resistance was obtained, known 
as a “metallized’’ filament, because it had a posi¬ 
tive resistance coefficient. 

The luminous efficiency of the carbon filament 
increases with its temperature, and carbon has 
the highest melting point of any substance — 








164 


EVERYDAY ELECTRICITY 


7,000° F. In the incandescent bulb, however, 
other factors enter, and the carbon filament ac¬ 
tually operates on a lower plane of efficiency. In 
the first place, the current, as it passes, volatil¬ 
izes the carbon and deposits it on the glass of 
the bulb, so that the carbon filament is decreased 
in size until the breaking point is reached. In 
the next place, the bulb is blackened by the de¬ 
posit of carbon, and a diminished output of light 
results. 

Consequently, a step in advance was taken when 
it was found that the metallized carbon filaments 
were more resisting and could be operated at a 
higher temperature. These improved lights were 
familiar for a number of years under the trade 
name “ Gem ”, signifying “General Electric Met¬ 
allized ”, and they were widely employed until a 
higher-efficiency lamp with metallic filament took 
their place. 

The Tantalum Lamp. The first of the lamps 
successfully to use a high-resisting metal employed 
osmium, but this was superseded soon by tanta¬ 
lum, the melting point of which was about 5,100° F. 
(2,800° C.). A fine wire of this metal was placed 
in the exhausted bulb. However, the electrical 
resistance of tantalum was found to be too low, 
so that considerable wire had to be placed in the 
bulbs, involving difficulties in construction. In 
1910, 3.5 per cent, of all incandescent lamps sold 
used tantalum, and this marked the highest figure 


ELECTRIC LIGHTING 


165 


in their production, the tungsten lamp being in 
favor from that time. 

The Tungsten Filament. Before that date, or¬ 
ganized research was devoted to a thorough study 
of materials for filaments and of their preparation 
in useful form. One important result was achieved 
in 1906, when the first tungsten filaments were put 
upon the market in special lamps. These fila¬ 
ments were made by the squirted process, but 
they were very brittle; and the first lamps were 
found to be costly and fragile. 

Constant research and experiment, however, 
continued and it was found that after it had been 
treated, the metal tungsten (with a melting point 
of 3,200° C.) could be drawn into the finest wires, 
and possessed a tensile strength perhaps greater 
than that of any other material. Furthermore, 
means of installing and keeping the tungsten fila¬ 
ment from breaking were developed; and with 
filaments of many sizes and shapes, the tungsten 
lamp is now in practically universal use. These 
lamps are now so durable that they can be used 
even on street cars, or for similar service. United 
States government specifications require an aver¬ 
age life for tungsten lamps of 1,000 hours of 
burning, and in most cases this is exceeded. 

The tungsten filament is subdivided so that it 
can be used on various lamps, from the smallest, 
affording illumination w T ith a fraction of a lumen 
or a fraction of a candle, to such monster affairs 


166 


EVERYDAY ELECTRICITY 


as the 30,000-watt — 60,000-candle power incan¬ 
descent lamps developed in 1922 for use in mo¬ 
tion-picture studios. In these, the filament is 
made of tungsten wire, one tenth of an inch in diam¬ 
eter and 93 inches long, and constructed in four 
coils. Such a lamp furnishes light equal to the 
combined light from 2,400 electric lamps of the 



B-Bu/b G-Bufb T-Bu/b PS-Bu/b 

Fig. 67: Types of Incandescent-lamp Bulbs. — S = Straight-side bulb; 
O = Globular bulb; T = Tubular bulb; PS = Pear-shaped bulb. The 
manufacturer uses a number following the initials, to indicate the diameter 
in eighths of an inch. 


size commonly used in the American household, 
and consumes 30 kilowatts. This lamp, it is 
interesting to state, has a bulb 12 inches in 
diameter and 18§ inches high. 

Gas-filled Lamps. The monster lamp just de¬ 
scribed, in which this long tungsten filament was 
inclosed, was a gas-filled lamp; this use of gas 
being a departure that came in about 1914 and 






























ELECTRIC LIGHTING 


167 


resulted in a more brilliant light. Up to that 
time, the incandescent lamp had been made with 
an exhausted bulb; but it was found that if an 
ordinary tungsten lamp were filled with nitrogen 
or some other inert gas, such as argon, it could be 
operated at a very much higher temperature than 
with a vacuum, and with less deterioration of the 
filament. It was also found that the filaments 
could be of larger diameter. The high resistance 
required inside the bulb was obtained by making a 
helical coil. 

These gas-filled lamps, made of ever-increasing 
size, found wide application in such situations as 
out of doors and in public places where once the 
arc, either open or inclosed, was used. For street 
lighting, in particular, they proved themselves 
distinctly valuable and supplanted the arc, as 
they did not require any trimming or expensive 
carbons. 

Current Supply. Incandescent electric lighting 
in America now almost universally employs cur¬ 
rent at from 100 to 125 volts, and this applies to 
both direct-current and alternating-current cir¬ 
cuits. In Europe, a higher voltage, ranging from 
200 to 250, is used to permit a more economical 
distribution of power, but as a rule lower voltages 
are more economical when lighting exclusively is 
concerned. Of course, for small isolated plants, 
such as those for railway cars, belt-driven from 
the axle, or those found in rural districts, with the 


168 


EVERYDAY ELECTRICITY 


generator driven by a small gas or oil engine, a 
much lower voltage, ranging from 25 volts up, is 
used with special lamps. For a motor-car light¬ 
ing circuit, appropriate lights of small voltage are 
employed. 

The Three-wire System. With direct-current 
installations of any size, the usual method is to 
employ the three-wire system of distribution 



devised by Edison. In this system, in its simplest 
form, two generators are used, and the outgoing 
conductor of one circuit and the return conductor 
of the other are combined in a single wire known 
as “ the neutral.” The result is that between the 
two outside wires a voltage double that on the in¬ 
dividual circuit is obtained, and it is possible to 
use a 220-volt motor when 110-volt lamps are 
placed in either of the circuits between the outside 
and the neutral wire. The three-wire system also 






















ELECTRIC LIGHTING 


169 


saves considerable copper and is a very economical 
method of distribution. 

In large cities, three-wire mains extend from 
the power house or substation to the distribution 
points and enter the building, but usually are 
extended no further within the building than the 



centers of distribution. From such a distribu¬ 
tion point, two wires are run over each circuit; 
the aim being to divide the number of circuits 
between the two sides of the three-wire system as 
evenly as possible. 

Isolated Lighting Systems. An important de¬ 
velopment that has brought increased comfort 










































170 


EVERYDAY ELECTRICITY 


and convenience to many rural homes has been 
the independent generating set in which a small 
dynamo is direct-connected to a self-regulating 
gasoline engine. There are several systems in 
common use. In one, a storage battery is charged 
by the generator, being automatically cut off when 
fully supplied. In another, a small battery is 
used and the generator is started automatically as 
soon as a light or other load is switched on to the 
circuit. Various types of these installations are 
to be found, most of which have proven themselves 
eminently satisfactory under such extreme con¬ 
ditions of service as were encountered in tempo¬ 
rary buildings in the war zone during the World 
War. 

A number of these systems, particularly those of 
large capacity, operate at 110 volts, but in many of 
the smaller isolated lighting plants it is usual to 
operate at about 30 volts, or approximately one 
fourth of the ordinary voltage used in electric- 
light service. The reason for this is that such a 
system has a storage battery that is charged by a 
generator driven by a kerosene or other oil engine. 
When the system is operated at 30 volts, only 16 
cells of storage battery are required in place of 
three-and-a-half to four times as many cells if the 
120-volt system of distribution were used. The 
advantage consists not only in the reduction of 
the number of cells required and the proportion¬ 
ately less care, but also in the fact that the bat- 


ELECTRIC LIGHTING 


171 


tery cells can be made thicker, permitting a longer 
life. Thus, both the initial cost and the cost of 
renewals are less. 

Wiring. In wiring a building, the usual arrange¬ 
ment is to have the supply wires enter at the cellar. 
If the wires are overhead, they are carried to in¬ 
sulators supported by brackets clear of the build¬ 
ing ; thence they are led to the cellar, and, care¬ 
fully protected, they pass through the walls and 



Fig. 70: Layout of electric-lighting outlets for a typical small house, arranged 
to provide even and efficient illumination and convenience of power. 


are connected with the distribution system. 
There must be a cut-out where the wires enter the 
building and at this point the supply company 
inserts its meter. The waring can be run through 
the building exposed (in what is known as “ open 
work ”); or in molding, concealed knob-and-tube 
work, rigid conduits, flexible conduits, armored 
cable for short runs, or flexible tubing, depending 
upon local ordinances or fire underwriters’ regu- 




























































172 


EVERYDAY ELECTRICITY 


lations. The wire itself must he of adequate size to 
carry the current, and must have proper insulation 
of rubber and rotten. It is essential that all joints 
be mechanically and electrically secured without 
solder, but in addition they should be soldered 
and covered with insulation equal to that on the 
conductor. 

Protecting the Circuit. Every wire carrying a 
current of electricity is heated by the passage of 
the current, so that care must be taken that the 
size of a conductor is regulated to the current it is 
carrying. Naturally, as in the case of a tungsten- 
wire filament and the heat element in an electric 
heater, use is made of the heat developed by the 
current. However, when heat is produced in an 
ordinary conductor, such as an insulated wire, if 
the conductor is of small size and the current suf¬ 
ficient, the passage of the current may soften the 
rubber insulation and even produce in the wire a 
temperature high enough to ignite inflammable 
material in the vicinity. Accordingly, the size 
of the conductors that are used for wiring a build¬ 
ing is very carefully regulated, and the National 
Board of Fire Underwriters has prepared a table 
specifying the sizes of wire that may be used under 
various circumstances so as to assure adequate 
safety. 

The Fuse. Although the wiring should be suf¬ 
ficient to take care of the circuit, yet various mis¬ 
chances and accidents are likely to happen, so 


ELECTRIC LIGHTING 


173 


that a current may flow through a very small re¬ 
sistance instead of through the appliances fitted to 
the line. Accordingly, this heating effect is used 
in a protective device known as the fuse, which 
acts just as the safety valve or fusible plug on a 
boiler. In other words, a small length of easily 
fusible metal wire of high resistivity is included in 
the circuit, and when the current rises to a point 
where it heats the metal sufficiently, it will melt 
the fuse wire (or link) and break the circuit. 

By arranging the size of these metal fuses, it is 
possible to regulate the amount of current that 
any one circuit can carry in safety. The “ blow¬ 
ing ” of a fuse is a frequent occurrence in any elec¬ 
tric installation, and the fuse is a very useful pro¬ 
tection in a home where flexible cords are likely to 
become worn or fixture parts exposed, or where 
access may be had to the conductors by workmen 
or others. The fuse link is made of a mixture of 
lead and bismuth. Once, the bare links them¬ 
selves could be used at the cut-outs or other points 
of protection; but now a type of fuse is required 
that is inclosed so that no damage will be done by 
the melting metal, or else a so-called “ fuse plug ”, 
which screws into a receptacle, is employed. It 
is essential that every circuit should be properly 
safeguarded and restricted to some such limit as 
600 watts. For example, a circuit of sixteen 40- 
watt tungsten lights should be protected by a cut¬ 
out such as a fuse. 


174 


EVERYDAY ELECTRICITY 


Automatic circuit breakers are also used to pro¬ 
tect a circuit, and consist of switches which con¬ 
trol the circuit by means of an electromagnet 
that becomes operative when a current of a cer¬ 
tain strength passes. The circuit breaker is, of 
course, more elaborate and expensive than a fusi¬ 
ble cut-out, and is employed only on switchboards 
for large installations. 

Lamp Efficiency. It is customary to mark an 
incandescent lamp with the number of watts — 
that is, the power that it takes, and with the num¬ 
ber of volts — that is, the electrical pressure at 
which it is most efficient. Those familiar with 
the bill of an electric-lighting company will recall 
that electricity is paid for at so much per kilowatt 
hour; and as a kilowatt hour is simply 1,000 watt 
hours, it is possible to ascertain the cost of using 
an electric light by taking its rate capacity and 
multiplying it by the number of hours burned. 
For example, a 50-watt lamp in 20 hours would 
use 1,000 watt hours or one kilowatt hour; and if 
the cost for current is ten cents per kilowatt hour, 
the use of such a lamp would represent an expense 
of one half a cent per hour. 

A tungsten lamp is likely to give from .80 to 
1.00 candles per watt, whereas the old-fashioned 
carbon lamp would give but .25 to .33 and would 
cost practically three times as much for the same 
number of candle hours. In the case of the 60- 
watt lamp, for example, a carbon lamp gave but 


ELECTRIC LIGHTING 


175 


15 to 20 candle power, but a modern tungsten lamp 
would give over 60. In other words, for the same 
amount of current, from three to four times as 
much illumination is obtained with a modern 
lamp as with one of the earlier type, and the mod¬ 
ern lamp has a much longer life. 


CHAPTER XIII 

Applications of Electrical Energy 

The successful development of the electric 
motor in a wide range of sizes has wrought im¬ 
portant mechanical, industrial, and economical 
changes. Obviously, it is possible to utilize power 
wherever the necessary conductors can be car¬ 
ried, and this may be to a considerable distance 
with modern forms of high-tension transmission. 
Electricity has no economical competitor for the 
transmission of power. Attempts to use com¬ 
pressed air or steam or hydraulic pressure have 
been unsuccessful. On the ordinary electric cir¬ 
cuit, it is possible to use mechanical energy for a 
number of purposes that previously either were 
entirely neglected, or required manual effort, or 
in larger installations involved the use of a steam 
engine. For many purposes, the gasoline engine 
can compete with an electric motor, and it is, of 
course, available where there is no source of elec¬ 
tric supply. Generally speaking, the electric 
motor is able to drive either an individual machine 
or a group of machines with economy through the 
elimination of transmission losses in shafting or 
belting; and its economy has an added feature, 


APPLICATIONS OF ENERGY 


177 


inasmuch as the energy consumed depends upon 
what is actually required and does not involve an 
engine and boiler kept under steam. 

One has only to visit a modern factory where 
there is an individual motor for each machine, and 
notice the conditions of increased quiet, light, and 
cleanliness over those prevailing wdien shafts and 
belting were employed. It is now possible to 
locate electrically driven machines with due re¬ 
gard to the convenience of the process or the opera¬ 
tor, quite independently of the permanent lines 
of shafting once required, so that machinery can 
be distributed on the most convenient and practi¬ 
cal basis and adjusted to conditions of light, tem¬ 
perature, and so on. Furthermore, portable ma¬ 
chinery can be brought directly to the shop and 
used, connection being made permanently or tem¬ 
porarily with the nearest power outlet. The elimi¬ 
nation of belting gives increased headroom in the 
factory, resulting in better illumination and ven¬ 
tilation, and also affords considerable saving of 
space. The time and material required for oiling 
the shaft bearings, and the resultant dripping, 
are done away with, as is, of course, the very 
real danger of moving belts and pulleys to the 
workers. 

By the use of electricity in an industrial plant, 
the supply of power can be centralized at a single 
point and generating economies developed; or 
under certain conditions, power can be secured 


178 


EVERYDAY ELECTRICITY 


from an outside source entirely independent of 
the plant. In a small plant where the load is 
variable, and also in the case of one located in a 
city where space is costly or limited, this is a very 
serious consideration and has led to important 
developments in small special industries that re¬ 
quire no large installation of power but must 
have power constantly available. 

On the other hand, under some conditions, 
power can be produced directly very favorably 
and economically, especially in the case of a large 
hydroelectric development. Whether an isolated 
plant or a supply from the central station is pref¬ 
erable, is a matter that the managers of each in¬ 
stallation must take into consideration. 

The electric drive offers the additional advan¬ 
tage that a breakdown usually can be restricted to 
a single machine and is not extended to an entire 
group of machines or a whole building; and even 
should the electric power supply fail, as sometimes 
happens, provision is generally made for its dupli¬ 
cation. Under modern conditions, even when there 
is a failure of supply, due to some accident, it is 
quite common to connect with other sources ; 
and especially in cities and industrial centers, it 
is usually possible to obtain emergency service 
through a network of stations and supply sys¬ 
tems. 

Furthermore, with an electric motor, it is possible 
to determine the performance of any individual 


APPLICATIONS OF ENERGY 


179 


machine by the use of a recording or indicating 
meter, so that the cost of power of the individ¬ 
ual unit is determined and each unit is kept in 
the most satisfactory operating condition, any 
inefficiency being determined and checked. Mod¬ 
ern machine-shop conditions demand that all 
large machines employed on intermittent service 
should be equipped with individual motors, and 
the efficiency of these motors must, of course, be 
carefully studied as it has a bearing on the econ¬ 
omy of the plant. 

In practically every form of industrial activity, 
it is possible to use electric power and to employ 
the electric motor advantageously. So general 
is this that any catalogue of such uses would be so 
large as to cover the greater part of mechanical 
engineering. In the mine, from the electric drills 
and cutting tools to the electric cars, there is a 
wide range of applications. In all forms of han¬ 
dling machinery, hoists, and conveyors, the elec¬ 
tric motor can be applied advantageously and its 
use is very general. In the logging field and the 
lumber mill, electrical apparatus finds extensive 
employment, particularly where it is possible to 
use the sawdust and other refuse as fuel. In the 
cement industry there are many applications of 
electric motors, and metallurgical plants employ 
such motors for various kinds of machinery used 
in treating ores. In the textile industries, the 
motor has wrought many revolutions in machinery 


180 EVERYDAY ELECTRICITY 

and operation, and the same is true of the laundry 
industry. 

One can hardly mention any application of 
power in which the electric motor cannot be used 
to advantage, and the engineers of the great man¬ 
ufacturing companies are constantly engaged in 
finding new fields for their machinery or in adapt¬ 
ing special forms of motor to existing machines 
and processes. No matter how large or how small 
the power requirement, invariably a motor can be 
found that will meet the demand, and, as already 
indicated, with a surprising degree of economy. 

Electric Elevators. It may not be realized that 
it is the electric motor that has made possible the 
modern “ skyscraper.” Without means of access 
to its upper stories, such a structure would be 
worse than useless. The first elevators placed in 
office buildings were hydraulic, and for many 
years such machines, modified in numerous im¬ 
portant respects, prevailed. To-day, the mod¬ 
ern elevator is generally driven by an electric 
motor. The limit of height reached in such eleva¬ 
tors is represented by those in the Metropolitan 
Life Building and the Wool worth Building, New 
York City, with height of travel of 586 feet, 5J 
inches, and 679 feet, 10^ inches, respectively. 

In general there are two main classes of eleva¬ 
tors : freight and passenger; the division being 
on the basis of speed and capacity, as well as of 
character of service. The freight elevator oper- 


APPLICATIONS OF ENERGY 


181 


ates at a speed of about 75 feet per minute, and 
there is not in its case the frequent starting and 
stopping that characterizes the passenger car, 
which must run at a speed of from 250 to 500 feet 
per minute, or even more. 

For elevator motors, either direct current or 
alternating current can be used; but the system, 
whichever it is, must lend itself to ready control 
and quick response to the operation of the car 
switch. There must also be a number of safety 
devices, so that when the speed of the car exceeds 
a certain amount it shall be gradually retarded — 
first, by means of a centrifugal governor, and then, 
if that fails to act, through a mechanical governor 
that will break the circuit. Such action also 
takes place at the upper and lower limit stops, so 
that the car will not strike against the bottom of 
the shaft with undue force or be brought to the 
top with violence sufficient to free the cables. 

Electric elevators are divided, mechanically 
speaking, into four main classes: (1) drum type; 
(2) worm-gear traction type; (3) helical-gear 

type; and (4) gearless-traction type, this being 
subdivided into the (a) direct-drive (one-to-one) 
and ( b ) two-to-one varieties. 

In the gearless elevator used in such buildings 
in New York as the Singer Building, the Metro¬ 
politan Life Insurance Company Building, and 
the Woolworth and Equitable buildings, the gen¬ 
eral arrangement is as in the diagram (Figure 71). 


182 


EVERYDAY ELECTRICITY 


Its success depended upon the development of an 
efficient slow-speed motor. As will be seen, the 
cables above the car pass around the driving 
sheave, then around an idler sheave, and then, 
after a half-turn around the driving sheave, go to 

a counterweight. To the car 
and counterweight are at¬ 
tached compensating cables, 
so that the system is ap¬ 
proximately in a condition of 
equilibrium and the passen¬ 
gers on the car contribute 
the excess weight that must 
be handled by the motor 
operating the driving ma¬ 
chine. The usual arrange¬ 
ment is to place the electric 
motor directly over the hatch¬ 
way. The winding of the 
cables around the driving 
shaft and the idler sheave 
supplies enough tractive effort 
to drive the car. The motor 
used is of the slow-speed shunt 
type, and the arrangement has been found particu¬ 
larly adaptable for high-speed express service in 
the New York tower buildings. With it is com¬ 
bined a so-called micro-drive, which automatically 
levels the car platform with the floor landing after 
the operator has brought the car to a stop. 



Fig. 71: Diagram showing 
the mode of operation of a 
traction elevator. 









APPLICATIONS OF ENERGY 


183 


Numerous electric elevators are made with 
which a relatively high-speed motor is used, a 
double worm-and-gear drive being interposed be¬ 
tween the armature shaft and the cable drum. 
Such an arrangement is installed in the basement 
of buildings, rather than at the head of the hoist¬ 
way as in the case of the gearless traction type. 

Automatic Elevators. Whereas the high-speed 
elevator has made possible the skyscraper, auto¬ 
matic elevators have brought considerable comfort 
and convenience to private dwellings and other 
buildings by means of push-button control, thus 
eliminating an operator. These elevators repre¬ 
sent the most complete and ingenious attempts to 
provide all possible safety devices, as well as a 
control so complete and simple that a child may 
operate the car with absolute safety. The usual 
system is to install a push button on each floor at 
the door to the elevator shaft, and the circuit 
closed by this means serves to bring the car to the 
floor level; it being impossible to open the door 
until the electric latch is released by the car at the 
proper level. Once the door has been opened and 
the car entered, both the door of the landing and 
the door within the car itself must be closed. The 
push button within, connecting with the control¬ 
ler by a cable, will operate the motor to take the 
car to the desired floor; when that has been 
reached, the reverse of the foregoing operation 
must be followed. These elevators, although 


184 


EVERYDAY ELECTRICITY 


restricted to dwellings in some cities, in others are 
finding increased application to small office build¬ 
ings, hospitals, and other places where light, inter¬ 
mittent service is all that is required. 

Elevator Auxiliary Devices. In addition to 
affording the motive power and control for eleva¬ 
tor systems, electricity makes possible an elab¬ 
orate series of indicators and devices intended to 
call the attention of the operator to the particular 
floor at which a passenger desires to ride; and at 
the same time on the various floors it operates 
indicators showing the progress of each car. In 
the larger office buildings, a telephone installa¬ 
tion is provided, so that the starter is in communi¬ 
cation with the operator and can control the prog¬ 
ress of the cars. 

Electricity on the Farm. The farmer no less 
than other people has benefited by the use of elec¬ 
tricity, and it now is generally available, even on 
the small farms, through the use of compact iso¬ 
lated units in which the generator is driven by an 
internal combustion engine. However, the farmer, 
like others, may have the opportunity to avail 
himself of electricity from a central station; and 
if the power line passes his door, he may, by means 
of an individual transformer, obtain current for 
such purposes as seem to him good and sufficient. 

Of course, lighting is now generally possible. 
It is referred to elsewhere in this volume. There 
are, however, about a farm a number of other 


APPLICATIONS OF ENERGY 


185 


uses to which power can be applied with advan¬ 
tage. For example, running water is an essential 
on a farm ; and if the source of supply is a well or 
a distant stream, the pumping is an important 
problem. Water is required about the farmhouse 
not only for the kitchen and the sanitary pur¬ 
poses that modern conditions of living demand, 
but for the stock, in the dairy, and for washing 
and other purposes. Here again a gasoline pump 
can be, and often is, used; but with an electric 
pump there is no concern beyond turning on the 
current and seeing that the machine is properly 
lubricated. Such a pump can be used in connec¬ 
tion with a pressure tank, and the farmhouse may 
have as complete a running-water system as has 
any town dwelling connected to a public supply. 

The pump can be arranged to work automati¬ 
cally when the pressure falls, or, if a gravity sys¬ 
tem is employed (which is often the case), when 
the level goes beyond a certain point. With the 
isolated unit, the pumping can be done by using 
the generator or storage batteries when not called 
upon for lighting. With an outside supply, no 
thought need be given as to the availability of the 
current. 

The farmer also needs power for grinding his 
feed, cutting his ensilage, milking his cows, oper¬ 
ating his cream separators, churns, and other ap¬ 
pliances. For cutting wood and doing various 
jobs in the farm shop, electric power is a great 


186 


EVERYDAY ELECTRICITY 


timesaver. Reference is made to this on account 
of the fact that on the farm there always has been 
a large amount of manual labor for both men and 
women, and this has acted against the attractive¬ 
ness of the life, and, with the increase in the cost 
of labor, has made the undertaking less remunera¬ 
tive and efficient. 


The availability of electricity on the farm is 
shown by the accompanying list prepared by one 
of the leading manufacturers, under the heading, 
“ Some things one cent’s worth (l£) of electricity 


will do.” 


Shell corn. 

. . . . 8 

Grind corn. 


Cut fodder. 

. ... 200 

Cut ensilage .... 

. ... 300 

Thresh barley .... 

. . . . 1 

Separate milk .... 

. . . . 60 

Churn butter .... 

. . . . 33 

Groom horses .... 

. . . . 2 

Milk cows. 


Stuff sausages .... 

. ... 200 

(and innumerable 

other things) 


bushels 

bushel 

pounds 

pounds 

bushel 

gallons 

pounds 


pounds 












CHAPTER XIV 


The Transmission and Distribution of Elec¬ 
tricity 

By “ transmission ” is meant the delivery of 
considerable quantities of energy over consider¬ 
able distances, as distinct from “ distribution ”, 
by which is implied the supply of power in small 
amounts at numerous points to the ultimate con¬ 
sumer. In transmission, therefore, is involved 
the use of high voltages for the current, and neces¬ 
sarily a transmission line requires special arrange¬ 
ment for the conductors as regards their support 
and insulation. 

To-day, the United States is reaching an indus¬ 
trial stage in which power costs are becoming pre¬ 
eminent, in view of the high charges for fuel and 
its transportation. Industrially, the further de¬ 
velopment of the United States depends in no 
small degree upon the production of power at the 
lowest possible cost and its efficient transmission 
in the form of electrical energy to the point where 
it is needed. Just now, the practical limit of such 
transmission is about 250 miles, and there are 
efficient lines operating over such distances; but 
what the future has in store is hardly within the 


188 


EVERYDAY ELECTRICITY 


bounds of present-day engineering knowledge to 
prophesy. 

Long-distance transmission of power by elec¬ 
tricity is of comparative recency. To realize this, 
one has only to go back to 1890, when a small 
pioneer transmission line was built at Telluride, 
Colorado. This installation had vast practical 
significance, though it was only about three 
miles in length. It consisted of a single-phase 
alternator driven by water power, and it trans¬ 
mitted current at 3,000 volts along a line to the 
distant point where it was utilized in a single¬ 
phase alternating-current motor. This trans¬ 
mission system was selected in preference to a 
direct-current plant, which was also proposed, 
since it was found that in the latter case the 
amount of copper demanded for the line wires was 
so much greater that the project was impossible 
of realization. This installation was notable both 
as the first of the type and as showing that alter¬ 
nating-current high-voltage transmission not only 
was feasible but was economical and in every way 
practicable. 

The transformer is the heart of alternating-cur¬ 
rent transmission, for upon this depend the volt¬ 
age used on the line and also the nature of 
the conductor over which the power can be 
sent. We may be able to put 2,200 volts from our 
generator into the primary; and if our transformer 
is properly constructed, we can take out at the 


TRANSMISSION 


189 


secondary many more volts, even up to 220,000. 
Naturally, a high voltage is employed so as to 
reduce the loss along the transmission-line con¬ 
ductor, and hence its size and cost; for with a 
high voltage, a current can be sent over a compara¬ 
tively small copper wire without substantial loss. 

The usual arrangement is to raise the voltage 
1,000 volts for each mile of line up to 100,000 volts; 
but above that figure, new factors enter into the 
calculation, chief of which is the extra cost for 
poles and insulators for the high-tension conduc¬ 
tors. Should there be a breakdown and ioniza¬ 
tion of the air, there will result a loss of energy on 
the transmission line, but this may be guarded 
against in large measure by the employment of 
heavier conductors and by the placing of the wires 
at greater distances from one another, these 
changes naturally requiring a larger and stronger 
tower. 

At the distant end of the line, other alternating- 
current transformers are used that reduce or step 
down the voltage from the transmission value to 
that desired for distribution, so that the current 
can be utilized in the various consuming devices 
(such as synchronous converters) to supply direct 
alternating-current motors, or alternating-current 
lighting circuits. 

At the source of power (say, a waterfall or a 
reservoir), the usual arrangement is to have one 
or more hydraulic turbines direct-connected with 


190 


EVERYDAY ELECTRICITY 


alternators of appropriate capacities, the shaft of 
the turbine being connected with the rotor of the 
alternator. Naturally, the tendency at stations 
of large capacity is to increase the size of these 
units, but the amount of head under which the 
water is delivered and the volume available for 
a single unit will condition the size of the turbine 
and the capacity of output of the generator. 

Nature of the Current. The current produced 
and transmitted over a transmission line may be 
either single-phase, two-phase, or three-phase; in 
each case coming, of course, from the appropriate 
type of alternator. For each of these systems, a 
different arrangement of conductors is required. 
For a single-phase current, two wires are employed, 
whereas for three-phase, which is the most em¬ 
ployed, there must be three conductors. For the 
two-phase system, four wires are used. 

The single-phase current, which was the first 
employed, does not lend itself so readily to power 
circuits, inasmuch as single-phase motors are 
started less easily than those of other types, and 
are on the whole considerably less efficient and 
more expensive per horsepower than the very 
simple and much used three-phase induction 
motors, which now render satisfactory service in a 
large range of circumstances. The three-phase 
system is most used because it is the most economi¬ 
cal in the amount of copper required for the trans¬ 
mission line, and this is the largest single element 


TRANSMISSION 


191 


in the installation, outweighing the cost of the 
generator or the transformers. 

Conductors and Insulators. The conductors used 
for a transmission line are of either copper or 
aluminum, the latter metal on account of its 
lightness often being employed in the interests of 
economy on long lines. When the wire is of cop¬ 
per, it is solid and ranges in size from Number 2 
Brown and Sharpe gauge (0.258 inches in diameter) 
to Number 000 gauge (0.410 inches in diameter). 
For an aluminum conductor, there is usually a 
steel core around which strands of aluminum wire 
are laid. 

The conductors are carried on insulators of 
glass or porcelain mounted on pins on the cross 
arms of the supporting poles or towers, though 
sometimes in the case of the high-tension lines the 
conductors are carried suspended from the cross 
arms by suspension insulators, which are con¬ 
nected in a link-like arrangement. For the lower- 
voltage lines, wooden poles carrying wooden cross 
arms, on which are placed wooden pins for glass 
or porcelain insulators, are the usual form of con¬ 
struction, and such an arrangement suffices when 
the voltage does not exceed 60,000. For such a 
line, it is quite usual to space the poles about 100 
to 150 feet apart and to have two cross arms. This 
makes possible duplicate transmission lines on 
each side of the pole, so that the line has increased 
capacity and reliability. 


192 


EVERYDAY ELECTRICITY 


With the higher-voltage lines, steel poles whose 
height and design depend upon the nature and 
capacity of the line are employed. These may 
range from simple latticed construction with cross 
arms to elaborate towers rising to a height of from 
40 to 60 feet or more and spaced from 400 to 600 
feet apart. In such cases, the cross arms usually 
carry a duplicate transmission line arranged on 
suspension insulators. Towers have been built as 
high as 350 feet, a notable instance being afforded 
by those of the Shawinigan Power Company of 
Quebec, which carry copper conductors hung from 
steel cables. 


i 


CHAPTER XV 


Electricity and Transportation 

During the nineteenth century, the develop¬ 
ment of transportation contributed much to the 
progress of civilization. Different inventors early 
tried various arrangements of electromagnetic 
engines to propel small cars or vehicles, but they 
were hampered by the fact that their source of 
current was an electric battery. This was ex¬ 
pensive to maintain and its output of energy di¬ 
minished very rapidly. By 1879, however, genera¬ 
tors were built capable of furnishing current to 
motors of fair size; and from this time, the elec¬ 
tric railway made continuous development and 
progress. 

In Europe, von Siemens, and in America, 
Thomas A. Edison and Stephen D. Field, were ac¬ 
tive in their experiments, and von Siemens actually 
constructed both third-rail and overhead-wire 
lines in Germany. In America, a Field-Edison 
electric locomotive, deriving its current from a 
third rail and operating on a line 1,500 feet in 
length, was shown at the Chicago Railway Ex¬ 
hibition in 1883. Later in the year, C. J. Van 
Depoele built an overhead line, and experimental 


194 


EVERYDAY ELECTRICITY 


conduit lines were also devised. The first practical 
overhead trolley line was built in Kansas City in 
1884, and then in 1887 a 13-mile system of 
street railways for electric traction was installed 
in Richmond, Virginia. 

To-day, we have the electric railway all about 
us. It has wrought material changes in our lives 
and habits, and with its increasing application to 
trunk-line transportation, there are destined to 
be no less important developments. 

Electric Railway Motors. To supply current 
to the moving car and to develop an efficient 



Fig. 72 : Simple Circuit of an Electric-Trolley Line. 


motor were the two basic problems connected 
with electric traction, and these were early solved. 
The overhead trolley, by which an under-running 
wheel on the end of a jointed pole carried on the 
roof of the car came in contact with a suspended 
wire conductor, served to carry the electricity from 
the line to the motor. The return circuit was 
made through the wheels to the track and then 
through the ground, care being taken to bond the 
rails at the joints so as to obtain maximum con¬ 
ductivity. 

With the development of the electric motor, its 
application to the driving wheels of a car was, of 


























ELECTRICITY AND TRANSPORTATION 195 


course, a prime consideration. The earliest cars 
had on the platform a single motor geared by a 
chain to the driving axle, but soon more efficient 
types were developed carried on the trucks. 

The early motors were supplied with armatures 
that revolved so rapidly that it was necessary to 
have on the armature shaft a double reduction 
gear, or a small cog or pinion wheel, meshing into 
a larger gear wheel whose axle carried in turn a 
small wheel geared to a larger one on the axle of 
the car truck. These early motors were each of 
about 15 horsepower, and one to each car (as first 
employed) was found inadequate for all condi¬ 
tions of service. It was necessary to obtain the 
required increase of power by using a motor for 
each axle, or at least on each truck, and then 
transmitting the power of the armature directly 
to the axle by a single reduction gear. 

The first motors were of the series type and 
bipolar form, but with the development of motors 
for other service, it was found that here, as else¬ 
where, multipolar motors could be used with a 
corresponding and very beneficial decrease in the 
speed of revolution of the armature. Further¬ 
more, because of the hard service that electric 
car motors inevitably must experience, it was 
realized that everything must be done to make 
them as strong and substantial as possible. Con¬ 
sequently, the motors are inclosed and protected 
as much as possible; and in the inclosed type, 


196 


EVERYDAY ELECTRICITY 


largely used, the field magnets form a closed iron 
box, so that short-circuiting, from water or from 
metallic scraps or pieces picked up by the magnets, 
is prevented. 

About 1890-1891, single reduction gear motors 
were developed at the Westinghouse works, and 
in connection therewith was introduced a slotted 
armature that later became standard practice for 
all machines. In the usual single reduction gear 
motor, there are four poles, and a spring con¬ 
nection is maintained between the motor truck 
frame and the car frame. On one side of the 
motor truck frame, there are journals mounted 
on the projecting lugs that carry the motors; on 
the opposite side, there is a connection with the 
car truck by means of springs. On each armature 
shaft there is mounted a pinion, which is geared 
to the driving axle of the truck. The movement 
of the springs facilitates the starting of the car 
without shock as the motors turn through a small 
arc about the axles. In the gearless motor of mod¬ 
ern construction, the car axle passes through the 
armature shaft, which is a hollow tube; and from 
time to time, as desired, connection may be estab¬ 
lished by means of springs between the two so 
that they revolve together without loss of power 
in transmission. 

Current for Electric Railways. As electric trac¬ 
tion developed and motors and distribution sys¬ 
tems became standardized, it was found that direct 


ELECTRICITY AND TRANSPORTATION 197 


Three-phase Curner7f 


current at about 550 volts was the most available 
form of current supply for the trolley wires, and 
this became practically universal for the United 
States. This voltage was sufficient to cover a 
considerable extent of territory without producing 
a serious drop on the line before it reached the mo¬ 
tors. Overloading of the line will, of course, cut 
down the volt¬ 
age at each - . 

motor and give 
it less current. 

There was re¬ 
quired an ex¬ 
tensive and 
costly system of 
feeders to sup¬ 
ply the trolley 
wires. Conse- 



jA&AAJtr 


Ct/r/a/rT 


YorTrvJJe/lute 


1 i Fia. 73: Diagram showing the transformation of 

quently, wnen three-phase current, from a distant power supply, to 

a direct current by the use of a synchronous converter. 

the range ot 

electric traction was further extended, it became 
necessary to have a power station for each section, 
or (what later became more general) to have 
alternating current at high tension generated and 
distributed to a substation, where, by means of a 


synchronous converter, it could be reduced, trans¬ 
formed to direct current at 550 volts, and supplied 
to the line. The trolley wire was suspended from 
bracket arms or from cross wires properly insu¬ 
lated and carried on poles, and the feeders that 

























198 


EVERYDAY ELECTRICITY 


were required were also carried on these same 
poles. 

Conduit Electric Railways. In large cities, 
overhead trolley wires, even when carried on orna¬ 
mental poles, were not always pleasing to the eye, 
especially at crossings and junction points where 
there were a number of conductors. At the same 

sv*r time > the y were 

fa// p/otv RotV 

Tun 



a possible menace 
at times of snow 
sleet storms. 


Fig. 74 : Underground Trolley Conduit, 
with Rails and Conductor Rails. 


or 

and also were 
likely to interfere 
with the fire ap¬ 
paratus in case of 
fire. 

Accordingly, and in some cases on account of 
the cable conduits already existing, a form of 
construction was developed in which T-rails as 
conductors were carried insulated on yokes in 
conduits beneath and between the tracks; and 
from these rails, by means of contact pieces at¬ 
tached to so-called “ plows ”, the current was 
taken for the car-motor circuit. This construc¬ 
tion became standard in New York Citv and 
Washington, D. C., but at Budapest, Hungary, 
a system with side contacts was installed. The 
underground conduit, although it involved a 
greater expense, was at the same time less liable 
to interruption in the event of snow or ice storms. 



























ELECTRICITY AND TRANSPORTATION 199 


The feeders could be carried in the same or an 
adjoining conduit. 

Third-rail Systems. With the development of 
the trolley for concentrated and heavy service — 
as, for example, on elevated railways or subway 
systems, or at terminal yards and on main lines 
— it began to be realized that there was a point 
where the amount of current taken by each col¬ 
lector might be more than could be derived safely 
from a trolley wire, or where the amount required 
by one or more trains might be more than could 



Fig. 75: Third-rail system, with under-contact, as used on the New York 
Central lines in the New York “terminal zone.” 

be carried by suspended conductors of copper or 
aluminum. Accordingly, a third rail (or contact 
rail) was developed. In third-rail construction, 
the conductor, in the form of an iron or steel rail, 
is carried on insulators near the ground, so that 
there is furnished a continuous surface where 
contact may be made by a moving shoe attached 
to the car or locomotive, and whence current may 
be taken to the motor. A quite usual arrange¬ 
ment is to have a rail of standard section supported 
every few feet by substantial insulation carried 
on brackets or other supports. Provision is made 
for securing electrical continuity by bonding at 















200 


EVERYDAY ELECTRICITY 


the joints, and various forms of protection, in the 
way of wooden or other covers, are supplied 
against accidental contact. 

Third-rail construction is either top-contact, as 
in the case of the New York subways, the Penn¬ 
sylvania Railroad electrification around New York 
City, and the London tube railways; or it may be 
the under-contact form, such as is employed by 
the New York Central. Each arrangement, of 
course, necessitates a different form of contact 
shoe or collecting device attached to the car, and 
care must be taken in locating the contact rail 
ruth* exactly with re- 



spect to this ad¬ 
junct. 


Some cars and 
locomotives are 


Fig. 76: Diagram showing conductors as installed 
in London electric-railway tubes. The rails are not 
used for the return circuits. 


not equipped with 
combined top- 


contact and under-contact shoes, so as to be 
used interchangeably on different lines. Ordi¬ 
narily, the contact rail forms the positive con¬ 
ductor, the return circuit being by the track; but 
in the case of the London tube railways a negative 
contact rail is installed, which, although it in¬ 
volves greater first cost, is yet desirable under 
some circumstances. 

The third rail possesses many advantages; 
especially is it accessible for cleaning and repairs, 
as well as for inspection, and it is absolutely free 








ELECTRICITY AND TRANSPORTATION 201 


from lightning disturbances. It does not produce 
telephone and telegraph disturbances, nor induc¬ 
tive effects on the adjoining signal wires. 

Controlling Systems for Railway Motors. The 
usual arrangement, where the direct-current sys¬ 
tem is employed, is to control the speed of the 
motors either by introducing into the circuit suit¬ 
able resistance in series with them, just as is done 
with the ordinary starting box or rheostat of the 
simple electric motor, to reduce or increase the 
voltage; or to change the connections of the 
motors so that at first they will be in series, then 
(with the progressive movement of the lever) 
half of the line voltage will be applied to each, and 
finally such connections will be made as to permit 
the current to flow in parallel through all the 
motors, with the maximum in each one. 

At the controller box will be noticed a second 
or smaller lever. This is for reversing the direc¬ 
tion of the rotation of the motors, and is so ar¬ 
ranged as to change the direction of the current 
passing through the field coils. The terminals of 
the field coils of the motor are connected to the 
reversing switch, and this is made interlocking, 
so that the current switch must be brought back 
to the “ off ” position before the reversing switch 
will operate. This arrangement prevents the re¬ 
versal of current when there is voltage on the 
motors. Reversing switches are found with both 
alternating-current and direct-current equipment. 


202 


EVERYDAY ELECTRICITY 


The Multiple-unit Control. The control of a 
single motor of 25 horsepower will be appreciated 
as a very different matter from operating a num¬ 
ber of such motors simultaneously or managing 
those on a large locomotive. For example, the 
different motors on the cars of a suburban or sub¬ 
way train may exceed 400 horsepower in the aggre¬ 
gate, but their control must be effected from a 
single switch by a motorman. It will be apparent 
that for such an installation a controlling cylinder 
of contact points and movable switches for all the 
motors would not be possible on account of its 
abnormal bulk and the attendant dangers involved 
in concentrating so much vital apparatus at one 
spot. Accordingly, a master controller with op¬ 
erating handle, reversing lever, individual mag¬ 
netic blow-outs, and other adjuncts, usually is 
installed for multiple-unit control; and there have 
been developed several systems to accomplish 
this purpose. Among the more important of 
the adjuncts often found in such an installation 
is the so-called “ dead-man’s handle ”, which, if 
the motorman’s hand is removed from the button 
on the top, automatically interrupts the current 
and applies the brake, thus guarding against 
accident due to any sudden failure on the part of 
a motorman. 

In such a multiple-unit control system, through 
cables pass to each of the motors (or, in the case 
of a train, through its entire length) and connec- 


ELECTRICITY AND TRANSPORTATION 203 


tions are made with a motor controller that is in¬ 
stalled under each car in an iron box lined with 
asbestos. Here are located all the necessary con¬ 
tactors and the reversing switch for the circuits of 
that car, so that from the distant point where the 
master levers are situated, full control of the 
individual motors simultaneously is maintained, 
their starting, stopping, and speed being regulated. 

Alternating-current Motors. Various types of 
alternating-current motors have been in use for 
electric traction, and these present interesting 
problems in their control. When an alternating- 
current commutator motor is employed, it is usual 
to install a transformer, which takes the current 
at a line voltage of 11,000 volts or less and reduces 
it to the 400 or 500 volts required for the motors. 

In the case of motors designed to operate on 
either alternating or direct current (as in the loco¬ 
motives of the New York, New Haven and Hart¬ 
ford Railroad), the control apparatus is so ar¬ 
ranged as to cut out the transformer from the cir¬ 
cuit at the time when the train passes from the 
alternating-current to the direct-current con¬ 
ductors, and connect the motors for series parallel 
control. This requires also connected rheostats 
in the circuit, and a change in the field connections 
of the motors to operate with the direct current. 

In the case of this control system, there is also 
involved the changing of the air-compressor motor 
circuits and the circuits for train lighting. This 


204 


EVERYDAY ELECTRICITY 


somewhat complicated process all happens in a 
few moments, without stopping the train; and 
on some systems, it is done automatically when the 
transition space between the alternating current 
and the direct current is reached. 

When three-phase induction motors are em¬ 
ployed on electric cars or locomotives, the control 
is effected by varying the resistance of the sec¬ 
ondaries of the motors. The starting resistance 
is connected in the circuit through the collector 
rings, to which the secondaries of the motors 
(which have a definite winding) are connected. 

Magnetic Blow-out. It is, of course, necessary to 
protect the circuit on a railway car or locomotive, 
so that too much current will not flow and cause 
damage. The usual type of circuit breaker em¬ 
ployed is known as the magnetic blow-out type, in 
which auxiliary contacts are employed that open 
in a strong magnetic field, which serves to 44 blow 
out ” the arc formed at these contacts. The con¬ 
tacts are made of copper and are bridged by a 
laminated copper brush that opens when the 
breaker operates. When there are a few hundred 
amperes at 600 volts or less, this device serves to 
give adequate protection to a railway car. It is 
arranged with a discharge vent from the blow-out 
compartment, so that the vapors from the arc will 
not do any damage. 

Electric Locomotives. The success of the trolley 
car and the equipment of the trolley line were 


ELECTRICITY AND TRANSPORTATION 205 


well established before active efforts had been 
made to deal with the problems of heavy transpor¬ 
tation. The steam locomotive had established 
itself as a useful and in many respects efficient 
machine, though from the point of view of service 
rather than on the mechanical side. There were, 
however, classes of service in which its defects 
were distinctly apparent and produced discom¬ 
fort. These were, namely, at and about large 
terminals and for tunnel service. Modern termi¬ 
nal development began with the movement of 
traffic by electric locomotives through the tunnel 
at Baltimore in 1896, the first electrification of a 
steam road. The great terminals of the Grand 
Central and Pennsylvania stations in New York 
City were made possible by electrification, and 
their improvement developed large and valuable 
tracts of real estate with approved and modern 
buildings. 

From such terminal arrangements, electrifica¬ 
tion gradually extended so that on the New York 
Central the electric zone reached to as far north 
as Harmon, and the New YT>rk, New Haven and 
Hartford, which occupied the Grand Central 
terminal conjointly with the New York Central, 
carried electrification as far as New Haven, using 
the direct current of the New York Central system 
in the terminal proper, and the single-phase alter¬ 
nating current as far east as New Haven. For 
electric transportation, the direct-current system 


200 


EVERYDAY ELECTRICITY 


at 1,500 volts had made such a good record for 
itself that in 1922 it was selected for the electri¬ 
fication of the lines of the Illinois Central Railroad 
within the city of Chicago. The track miles in¬ 
volved in this undertaking total 125, including 
the suburban passenger service from Chicago to 
Matteson, 28 miles ; the Chicago branch, 4| miles, 
and the Blue Island branch, 4.4 miles; with a 
considerable extent of switching and freight 
transfers between the yards. Already direct cur¬ 
rent at 3,000 volts had been used on the Chicago, 
Milwaukee and St. Paul (as referred to later), 
two motors being arranged in series. 

Types of Locomotives. Once the electrification of 
tunnels, terminals, or main lines was decided 
upon, there came the question of electric loco¬ 
motives ; for obviously, the existing rolling stock 
of the different lines must be used and handled 
in trains of practically the same size and in much 
the same conditions as under steam-locomotive 
operation. In other words, there was required a 
concentration of large units — not a group of 
motors at the axle of separate cars, as on mul¬ 
tiple-unit trains. 

There have been various types of electric loco¬ 
motives developed for freight service and for 
through passenger service, but these vary con¬ 
siderably and no approximation to a standard 
design has been attained. Various electric sys¬ 
tems have been used, involving different voltages 




% > 





Westinghouse Single-Phase Locomotive Used on the New York, New 

Haven and Hartford Railroad. 



General Electric Company’s High-Speed Gearless Passenger Locomotive Used 
on the Cascade Division of the Chicago, Milwaukee and St. Paul Railway. 


ELECTRIC LOCOMOTIVES 































ELECTRICITY AND TRANSPORTATION 207 


and both direct and alternating current. There 
are three general types of drive used in American 
locomotives: 1. Motors geared directly to the 
axle; 2. Gearless motors mounted on or around 
the axle; 3. Geared or gearless drives in which 
the power is transmitted to the drivers by means 
of cranks and rods. 



F O 


Fig. 77: Types of American Electric Locomotives. — (A) Direct axle- 
geared drive. ( B ) Single-motor gear-and-quill drive. (C) Twin-motor gear- 
and-quill drive. (D) Direct axle-mounted armature drive. ( E ) Gearless 
motor quill drive. ( F ) Rod drive with gearless motor, as used at the Penn¬ 
sylvania Terminal, New York City. (G) Rod drive with geared motor, as 
used on Norfolk and Western freight locomotives. 

In the United States, the costs of coal and fuel 
oil, although they may not become as prohibitive 
as in Europe, are nevertheless an important factor. 
Not only must coal for the steam locomotive be 
carried in the tender, making additional weight, 
but in addition large supplies of coal must be 
transported to various coaling stations for use. 

It has been stated that the railway fuel carried 
by American railroads for supply and on the loco- 

























208 


EVERYDAY ELECTRICITY 


motive tenders forms a nonpaying load conserva¬ 
tively estimated at twenty per cent, of the total 
revenue tonnage. In the mountainous regions, in 
particular those of the Rockies and the Sierras, 
there is likely to be available water power but 
no coal, so that the coal required for the extra 
locomotives demanded to haul the trains over the 
heavy grades is an important consideration. Con¬ 
sequently, the Great Northern and the Chicago, 
Milwaukee and St. Paul now handle the trains 
over their mountain grades by electricity, and the 
Chicago, Milwaukee and St. Paul in 1922 operated 
electrically on the main line across five mountain 
ranges, a total of 660 route miles, formerly the 
most active part of the system. 

The railroad man realizes that electrification 
would substitute an unlimited for a limited motive 
power. Instead of the amount of power being 
restricted by that generated by the engine and 
the boilers carried, the electric locomotive can 
utilize the entire power-house capacity of the sys¬ 
tem. Two or more electric locomotives can be 
operated together with one crew, and any amount 
of tractive effort is- available for utilization in a 
single train. 

Furthermore, it is now possible not to stop at a 
maximum grade of two per cent., and also to have 
a greater range for the speed of freight trains, 
hitherto limited to the power of the steam loco¬ 
motive. To-day the freight train operated elec- 


ELECTRICITY AND TRANSPORTATION 209 


trically may be as long as its structural strength 
permits, or as long as may be handled in the yards 
or on the sidings. Likewise, schedule speeds may 
be increased to any point which the track equip¬ 
ment will stand with safety; and instead of being 
accelerated from a standstill at the rate of a quarter 
of a mile per hour per second, passenger trains 
may be accelerated at the rate of one to one-and- 
a-half miles per second. Furthermore, on steep 
grades, by means of so-called “ regenerative brak¬ 
ing”, power is returned to the distributing system 
by arranging the motors to act as generators. 

Up to 1922, not more than about one per cent, 
of the entire scheme of railroad mileage in the 
United States had been electrified. Moreover, it 
was unfortunately the tendency of railway adminis¬ 
tration to consider the more notable examples of 
special cases when offering the solution of a practi¬ 
cal problem. 


CHAPTER XVI 


Electricity on Shipboard 

For many years electricity had been used on 
shipboard, not only for lighting but for the vari¬ 
ous auxiliaries such as the cargo winches, ash 
hoist, refrigerating apparatus, ventilating fans, 
blowers, etc., both in the navy and in the merchant 
marine. In the navy particularly, electricity was 
found to be very convenient in connection with 
the equipment for elevating and training the guns, 
operating the ammunition hoists, and the many 
purposes associated with a warship. Accordingly, 
it was not strange that officers of the navy should 
seek to find some means of electrical energy for 
the propulsion of ships. The reciprocating engine 
was realized to be uneconomical and suffered in 
comparison with the steam turbine, but the turbine 
as applied to the propeller shafts required some 
form of reduction gear or other arrangement, 
which cut down the efficiency gained over the 
reciprocating engine. Naval engineers believed, 
however, that the steam turbine could be directly 
connected with an alternating-current generator, 
just as was the practice in the stations on land. 


ELECTRICITY ON SHIPBOARD 211 


and the current employed to drive one or more 
motors on the shaft; the speed of the ship being 
regulated by the control of the current. 

After various experimental installations were 
made, the United States Navy adopted this 
method for its new dreadnaught New Mexico , 
which was finished and placed in commission in 
1918. This was the first battleship to have elec¬ 
tric propulsion and marked an era in warship de¬ 
sign and construction. There were four two- 
phase turbogenerators of 11,000 kilowatts capacity 
each, which supplied the current to four induction 
motors of 7,000 horsepower each. To excite the 
generator fields, two 300-kilowatt generators were 
provided. A novel arrangement of the motors 
was a pole-changing feature that for high speed 
made it possible to use 24 poles on each motor; at 
speeds below 15 knots, 36 poles were employed. 
When both generators were running, 4,400 volts 
was the voltage of the output; and when only one 
was in operation, 3,000 volts. The New Mexico 
on her trial trip maintained a speed of 21.33 knots 
an hour. The design was followed in other Ameri¬ 
can battleships. 

Electricity plays an important part in the sub¬ 
marine and the submersible. Of course, when the 
ship is sailing awash, it is possible to use internal- 
combustion engines to drive the screws, and also 
to drive the generators and to charge the batteries; 
but once the hatches are closed, the motors must 


212 


EVERYDAY ELECTRICITY 


be called into play and the load of driving the 
screw transferred to the accumulator or storage 
battery. Upon the capacity and charge of the 
batteries, much of the efficiency of the operation 
of the submarine depends, and constant care is 
given them. When running submerged, a sub¬ 
marine in war time is, of course, drawing on its 
available capital, so that whenever there is oppor¬ 
tunity it comes to the surface and charges the 
batteries. 


CHAPTER XVII 

Electric Heating 

One of the principles early established by the 
British physicist, James P. Joule (1818-1889), a 
brilliant experimenter who forsook the brewing 
industry to carry on research, was that when a 
current flows through a resistance, heat is always 
dissipated in this resistance. This circumstance 
is very familiar in the electric heater, in the in¬ 
candescent lamp, and, in fact, in almost any de¬ 
vice that makes it possible to realize that with 
increase in current the coils or other parts become 
warmer. 

With an electric current, the heat developed in 
any conductor is directly proportional, first, to its 
resistance; second, to the square of the current 
strength; and third, to the time during which the 
current flows. In devices that are used on a con¬ 
stant, fixed electromotive force, the resistance 
is usually provided in the form of coils or ribbons 
of some high-resistance material of wire, either 
exposed or coated with a refractory composition. 

Electric Heating Appliances. In any electric 
heating device, the prime essential, naturally, is 
the heating unit, which consists of a coil or thin 
plate of high-resistance wire or ribbon to furnish 


214 


EVERYDAY ELECTRICITY 


the resistance. This wire or ribbon must be capa¬ 
ble of supporting a high temperature — that is, 
from 500° F., to 2,200° F. — without deterioration. 
The resistance wires used principally are alloys: 
German silver, nickel steel, nickel chromium, and 
copper nickel; to which list manganese and other 
substances sometimes may be added. 

If the heating unit is exposed directly to the 
air, a resistance material should be selected that 
is nonoxidizing; and for this purpose, nickel 
chromium, mentioned above, is often a very use¬ 
ful alloy. On the other hand, such alloys as nickel 
steel and German silver may deteriorate rapidly 
if exposed to the air. This effect, however, is 
counteracted by inclosing such a resistance wire 
in some fireproof material, as mica or clay. 

The ordinary type of small heating unit found in 
flatirons, chafing dishes, percolators, stoves, etc., 
has an incased disc in which the resistance ele¬ 
ment in the form of a wire or ribbon is wound on a 
mica base, or else it consists of a grid stamped from 
a thin sheet of the resistance alloy and mounted 
between thin sheets of mica. A heater of this type 
is often known as a “ monoplane heater ”, to dis¬ 
tinguish it from the open-coil type employed in 
toasters, grills, etc., in which the resistance wire 
is supported by an insulating material, such as 
mica or porcelain. 

To form still larger heating units, such as an 
electric radiator for a room, asbestos devices may 


ELECTRIC HEATING 


215 


be wound with wire and covered with a fireproof 
cement compound. The high-resistance ribbon 
may be wound on a mica cylinder to form what is 
known as the cartridge unit, the wire being coated 
with insulating fireproof cement and the unit be¬ 
ing inserted in a hole in the casting that is to 
transfer the heat to its point of utilization. These 
cartridge units are employed for discs, stoves, 
grids, and broilers. 

The Heating of a Room. Except where elec¬ 
tric energy is available at a very low rate, the 
heating of rooms and buildings by electricity is 
not feasible. However, it is possible to employ 
electric radiators for special service, as to warm a 
room for dressing, or in bathrooms and ticket 
booths; and to give an intermittent auxiliary 
service elsewhere, as in the temporary occupancy 
of dwellings or offices. It has been estimated 
that from one to two watts per cubic foot of volume 
will be required to keep an ordinary-sized room 
warm when the outside temperature is near the 
freezing point; and with electricity costing ten 
cents a kilowatt hour, the expense in the case of 
most installations would clearly be prohibitive. 
However, electric heaters can be fitted at once 
into a place where coal or gas stoves could not be 
readily installed or could not be employed for 
other reasons; and besides, they have a less fire 
risk, a greater cleanliness, and operate under 
better hygienic conditions. 


216 


EVERYDAY ELECTRICITY 


Electric Ranges. When current is available at 
a low rate, there is no question as to the ad¬ 
vantage of electric ranges, which are now made 
to cook for anywhere from two to several hundred 
people. In one type of electric range, there is a 
so-called “ hot plate ” in the top of the range, over 
which fit special flat-bottomed utensils with an 
apron or flange around the rim and a lock or clamp 
to afford good contact between the utensil and the 
plate. In others, there is provided a chamber 
in the top of the range, into which the cooking 
utensils are inserted, it being then covered by an 
ordinary stove lid. 

The usual construction for the ovens is to form 
them of light sheet steel and with double walls, 
the intervening space being filled with material 
that is a nonconductor of heat. On the important 
circuits, there are pilot lights to show when the 
current is on or off, and there are appropriate 
switches for each element of the range, with ther¬ 
mometers or thermostats, so as to secure exact 
control. 

Electric il Fireless Cooker.’’ Some of the most 
efficient devices that have been employed to con¬ 
serve the heat developed are found in the form of 
electric “ fireless cookers ” or electric ranges in 
which the “ fireless cooker ” idea has been in¬ 
corporated ; and such an arrangement, with 
jacketing and insulation of mineral wool or as¬ 
bestos, is found to-day in the best electric ranges. 


ELECTRIC HEATING 


217 


In one of these electric “ fireless cookers ”, there 
is employed a heating element of nickel ribbon 
surrounding the food compartment; this in turn 
is surrounded with an air-tight water jacket from 
which air has been exhausted; and surrounding 
the whole is heat-insulating material. 

The “ fireless cooker ” arrangement has been 
shown to be economical in that the current is on 
for only about one fifth of the time. Notwith¬ 
standing this, a sufficient temperature is main¬ 
tained for boiling, stewing, and steaming, which 
take a constant and intense heat and are the most 
expensive processes for an electric cooker. In 
other electric ranges, a system of thermostat con¬ 
trol not only maintains the temperature constant 
and at any degree desired, but cuts off or regulates 
the current when it is not needed and reduces 
the expense. 


Energy Demands of 

Typical Heating Appliances 

Flatiron .... 


Toaster .... 

. . . 450-550 

it 

Grill. 

... 600 

it 

Table stove . . 

... 600 

it 

Percolator . . . 

. . . 350-400 

it 

Water cup . . . 

. . . 300-500 

it 

Reflector radiator 

... 600 

it 

Hair curler . . . 

. . . 15-20 

it 

Warming pans 

. . . 25-50 

it 

Range .... 

. . . 5,000-8,000 

a 










CHAPTER XVIII 


Electrochemistry and the Electric Furnace 

In our consideration of the voltaic cell and of 
the electric current, it was made clear that chemi¬ 
cal energy may be transformed directly into elec¬ 
trical energy; or conversely, electrical energy 
may be transformed into chemical energy. A 
wide range of these activities is included in a 
science known as “ electrochemistry ”, which 
possesses important practical applications in many 
industries. On the industrial side, coupled with 
electrochemistry proper, are the phenomena in¬ 
volved in the use of the electric arc to obtain 
high temperatures and thus produce important 
chemical reactions; but these thermochemical 
phenomena, strictly speaking, should be con¬ 
sidered apart from those due to electrolytic 
processes. 

The work of Sir Humphry Davy in decompos¬ 
ing metallic salts into their elements, developed 
and extended by other chemists, early indicated 
that electrochemistry was a fertile field of science ; 
and soon this field was enriched in both theory 
and in research. The more practical applications 


ELECTROCHEMISTRY 


219 


naturally awaited the development of the dynamo 
in order to have adequate current to carry on 
operations on an industrial scale. For example, 
a solution of copper sulphate could be decomposed 
by an electric current and pure electrolytic copper 
obtained at one of the electrodes; but unless 
current was available in sufficient amount and at 
low cost, the electrolytic process naturally could 
not be used on a commercial scale. 

It was found possible to deposit various metals 
from solutions upon baser metals. Once the 
dynamo was available to give proper current, 
this could be done extensively; and in fact, it 
gave rise to many an important industry. 

Electroplating. Through the action of the 
electric current, gold, silver, copper, and zinc 
can be placed in a thin, smooth, compact, and 
adhesive coating upon a metallic surface of a 
baser metal, or upon a conducting surface espe¬ 
cially arranged so as to secure the advantage of 
the coating of a metal without that metal’s being 
employed for the entire construction. The pri¬ 
mary considerations are a solution in water of 
one of the salts of the metal to be deposited, and 
an anode or plate of this metal. The object to 
be coated or plated forms the cathode, being of 
course connected with the negative terminal of 
the current just as the anode is joined to the posi¬ 
tive. Naturally, the anode wears away in the 
process, whereas the cathode gains by the amount 


220 


EVERYDAY ELECTRICITY 


deposited from the liquid in the constant process 
of electrolytical decomposition that is taking place. 

If we fix in mind some of the articles that are 
made in this way, it may be possible to secure a 
better idea of the process. Gold plating is used 
for jewelry; and by it, coatings of varied thick¬ 
ness or of any desired color may be obtained. 
Silver plating is employed for tableware and other 
like objects, and in the best products the silver is 
deposited in a thick and firm coat. 

Nickel plating is used for many articles, es¬ 
pecially those of iron and steel, to prevent rust. 
Copper plating is likely to be employed for the 
same purpose, particularly for surfaces which 
have been temporarily made conductive by a 
layer of plumbago. Zinc plating is feasible, but 
has few if any advantages over coating an article 
with melted zinc. Brass or bronze plating can be 
used for various novelties, generally of an orna¬ 
mental character. 

The usual arrangement of a plating bath is to 
suspend in the electrolyte the objects to be plated, 
between two rows of cathodes; copper wires be¬ 
ing employed for the suspension and metal rods 
serving both as supports and as conductors for 
the current. The vats in which the plating takes 
place are usually of wood, lined either with lead 
or with some special resisting substance resem¬ 
bling pitch; or, in the case of small tanks, with 
porcelain. Inasmuch as small voltages are used. 


ELECTROCHEMISTRY 


221 


usually derived from generators supplying cur¬ 
rent at from five to six volts, the tanks are con¬ 
nected in parallel and are independent of each 
other, each tank usually being in series with a 
rheostat to regulate the voltage at the tank. 

In all plating processes, the surface to be coated 
must be rendered smooth and perfectly clean. 
The usual cleansing process involves, first of all, 
a bath to remove the grease, this bath being com¬ 
posed of a ten-per cent, solution of sodium carbon¬ 
ate or sodium hydrate. This is followed by a 
“pickling ” process, the object of which is to remove 
the oxide and to give a bright surface. The “pick¬ 
ling ” solution, which is a dilute solution of sul¬ 
phuric, hydrochloric, and nitric acids (sometimes 
with common salt and lampblack added), is 
washed off before the article is suspended in the 
electroplating bath. 

The nature of the bath and the process obviously 
depend upon the metal that is to be deposited; 
for industrial work, they are carefully determined, 
and a special technique is developed in each case. 
For nickel plating, the solution used consists of a 
solution of double nickel ammonium sulphate 
with ammonium sulphate in water; the anodes be¬ 
ing, of course, of nickel. For the proper current 
density in the bath, about two volts are required. 

For copper plating on zinc, iron, or tin, the bath 
used is of acid copper sulphate, with which is 
employed a solution of the double cyanide of 


222 


EVERYDAY ELECTRICITY 


copper and potassium. The voltage required is 
about three volts; and here, as in other electro¬ 
plating operations, the temperature of the solu¬ 
tion is an important consideration. 

For zinc plating and brass plating, appropriate 
baths are employed; that for brass plating being 
somewhat more complex, as not only the copper 
but the zinc has to be considered in the deposi¬ 
tion. For silver plating, the double cyanide of 
potassium and silver is used in preference to 
a solution containing silver nitrate, as the cyanide 
gives a smooth deposit and is susceptible of con¬ 
trol. It is not generally realized that silver is 
deposited on only copper or copper alloy, and that 
any object to be silver plated must either be of 
copper or be copper plated first. 

For gold plating, the electrolytic solution em¬ 
ployed is the double cyanide of gold and potas¬ 
sium, with free potassium cyanide in addition. 
About 1.45 volts are required to furnish a satis¬ 
factory current, and the anodes must be of pure 
gold. By depositing another metal at the same 
time in slight amount, the color of the gold de¬ 
posit can be varied and different artistic and other 
effects be secured. 

Electrotyping. The large editions of modern 
books are made possible by printing, not from the 
type originally set, but from a copper or nickel 
reproduction made by electroplating. This proc¬ 
ess, of course, can be used to reproduce any article 


ELECTROCHEMISTRY 


223 


of which a mold can be made in order to furnish 
an exact duplicate, as in the case of type. The 
printed page is derived from individual type char¬ 
acters or lines made of type metal, which is a mix¬ 
ture of lead, tin, and antimony. This metal, if 
used for direct contact with the paper, would not 
afford more than a limited number of satisfactory 
impressions, when the surface of the type would 
be worn and its record correspondingly affected. 

Accordingly, the page is arranged as if for print¬ 
ing, and then an impression of the type is made in 
wax. This mold is covered with graphite, finely 
powdered; and by means of soft brushes, a com¬ 
plete conducting coating of the entire mold is 
effected. Over this, iron filings are sprinkled, and 
then a solution of copper sulphate is poured. 
The iron enters into the solution and copper is de¬ 
posited, both on the filings and on the graphite. 
After it has been washed in water, the wax mold is 
suspended in a bath of copper sulphate, and cur¬ 
rent is allowed to pass until a film of copper has 
been deposited electrolytically on the graphite. 
This can be continued until a sheet of the desired 
thickness is obtained, which is then removed from 
the wax and backed up with a solution of type 
metal, so as to give it strength and body. This 
becomes the printing surface used on the presses 
and can be stored away for future use, thus re¬ 
leasing the type for other work. A current of 
from 0.75 to 1.50 volts is required for electrotyping. 


224 


EVERYDAY ELECTRICITY 


Refining Metals by Electrolysis. The electro¬ 
lytic refining of metals is, perhaps, the largest and 
most important application of electrochemistry. 
Here the metal to be refined is, in its impure 
state, made the anode of an electrolytic cell, and 
the cathode is a plate of pure metal upon which the 
ions are deposited. The electrolyte is a solution of 
the salt of the metal, and at the outset of the pro¬ 
cess should be pure. The action of the current is 
to cause the metal at the anode to dissolve, to¬ 
gether with certain of its impurities that are elec¬ 
tropositive with regard to the principal metal. 
Those that are electronegative remain at the anode, 
from which they may drop off to the bottom of 
the tank, to be recovered later; or some may be 
dissolved by the free acid, and others precipitate 
as an insoluble salt. 

Copper Refining. The most important instance 
of refining metals electrolytically is that of copper, 
by which process practically all of the copper 
used for electric wires is obtained in a purified 
form that may approach 99.95 per cent. Further¬ 
more, in this process the precious metals contained 
in the crude copper are also reclaimed; and this 
is an important item, as the crude copper anodes 
used at American refineries may contain per ton 
as much as 300 ounces of silver, 40 ounces of gold, 
and 0.2 per cent, of arsenic. 

The electrolyte used in copper refining is a solu¬ 
tion of copper sulphate and sulphuric acid con- 


ELECTROCHEMISTRY 


225 


taining from 4 to 10 per cent, of free acid, and 
from 12 to 20 per cent, of copper sulphate. Special 
tanks are arranged to provide for the circulation 
of the electrolyte, and different forms of arranging 
the electrodes have been developed. The voltage 
used in each cell ranges from 0.1 to 0.3. 

Nickel is refined electrically by using a weak 
acid solution of nickel chloride or nickel sulphate. 
This process is employed when very pure nickel is 
desired for special purposes. Likewise, elec¬ 
trolytic processes are used for separating silver 
and copper, and also for the refining of gold. 
Lead refining is carried on with an electrolyte that 
is a solution of lead fluosilicate. By the elec¬ 
trolytic processes, other metals, such as mercury, 
tin, bismuth, and antimony may be separated, 
but the commercial processes with these are not 
of special importance. 

In addition to the electrolytic processes in¬ 
volved in the use of the electric furnace, later to 
be discussed, there have also been efforts made to 
obtain metals directly from the ores by electro¬ 
lyzing the solutions in which the ore is formed into 
an electrolyte, through dissolving them in acid or 
in some other chemical arrangement. Processes 
also were developed for extracting lead and zinc 
from various ores, and a rather important indus¬ 
try is the recovery of tin from tin scrap and from 
tin cans. 

The electrolytic method of treating the tin 


226 


EVERYDAY ELECTRICITY 


scrap, to which the old cans after cleaning have 
been reduced, consists of suspending them in a 
solution of sodium hydrate containing a certain 
amount of carbonate (absorbed from the air) and 
sodium stannate, the latter being a tin compound. 
This tin scrap, suspended in baskets of perforated 
sheet iron, is, of course, the anode, and the cathode 
is formed of iron sheets. Under the action of the 
current, the tin is dissolved at the anode and is 
deposited on the cathode as spongy tin. This 
later is compressed by a hydraulic press into small 
cylinders, subsequently to be melted in a furnace. 
The removal of the tin at the anode is accomplished 
so completely when the process is properly con¬ 
ducted that the iron is valuable for use in open- 
hearth plants. 

Chemicals from Electrolytic Processes. Since the 
time when Sir Humphry Davy derived metallic 
sodium and potassium from salts of these metals 
by electrolysis, there have been important develop¬ 
ments, and not only can these metals be obtained 
in a pure state, for which there is a comparatively 
limited application, but also materials of vast 
commercial importance. One of these is sodium 
hypochlorite, or electrolytic bleach, which is ob¬ 
tained by the decomposition of sodium chloride. 
Other substances are obtained, such as chlorine, 
which is available for use in making bleaching 
powder, and caustic soda, which has an extensive 
industrial use. These various electrolytic proc- 


ELECTROCHEMISTRY 


227 


esses for potassium or sodium chlorite have 
been very highly developed, and there are special 
forms of cells for use in making the different 
products. 

Electric Furnaces. The electric arc, which we 
have already referred to as a source of light of 
intense brilliancy, possesses nowadays an even 
more important application on account of its heat. 
It was early found that in the arc between the 
carbon electrodes even the most refractory metals 



Fio. 78: Cross section of the HSroult electric-arc furnace, showing carbon elec¬ 
trodes and a charge of metal that is melted by the heat of the arc. 

could be melted. Accordingly,, as soon as large 
currents were available, various forms of electric 
furnaces were developed in which use was made 
of this property and special constructions were 
contributed. 

In addition to the arc furnace, it was found that, 
by bringing to bear the principle of the trans¬ 
former, the material to be heated could be sub¬ 
stituted for a low-tension winding, and a heavy 
current applied to the higher tension. In other 

























































228 


EVERYDAY ELECTRICITY 


words, there was obtained what was known as 
the “ induction furnace”. Then, in the third 
leading type, namely, the resistance furnace, the 
furnace charge is heated by means of the current 
and the heat developed by this resistance is used. 
But the electric furnace is useful not only for 
its intense heat or thermic effects, but also for the 
fact that electrolysis can take place at a high 



Fig. 79: Diagrammatic Section of an Induction Furnace. 


temperature just the same as in an electrolyte at 
the usual temperature. 

The electric furnace has a distinct advantage, 
which we have seen already applied to the utiliza¬ 
tion of electrical energy in general, namely, that 
an intense temperature can be produced directly 
at the point of utilization. Furthermore, this tem¬ 
perature is greater than that of a combustion fur¬ 
nace. For example, the hottest part of the posi¬ 
tive carbon of the electric arc is stated to be 
between 3,900° C. and 4,000° C., whereas in an 



























ELECTROCHEMISTRY 


229 


ordinary furnace the temperature developed is 
considerably less. 

An electric furnace requires some special form 
of construction to contain the hearth or the cruci¬ 
ble, and to protect this portion from loss of heat 
by radiation and conduction. The electrical en¬ 
ergy is used, first, in heating up the furnace; then 
in raising the temperature to a degree where the 
charge is melted or vaporous; then in adding the 
heat required for the reaction; and finally, in 
supplying the heat losses. 

Considerable attention has been paid to the de¬ 
sign and construction of electric furnaces; and 
with their increased use for open-hearth steel re¬ 
fining, furnaces of large size have been built. A 
notable installation was that of the United States 
Naval Ordnance plant at Charleston, West Vir¬ 
ginia. Two similar furnaces had a capacity of 
40 tons each, and were especially adapted for de¬ 
livery of steel of special characteristics and com¬ 
position. 

The electrodes used in an electric furnace are 
composed of carbon graphite, and the aim is to 
have them as short and of as large cross section as 
possible, in order to cut down the loss due to elec¬ 
trical resistance. Various arrangements are made 
of the electrodes. Sometimes both are placed 
horizontally, whereas at other times, as in the case 
of the Heroult furnace, there is a vertical elec¬ 
trode above a carbon crucible. 


230 


EVERYDAY ELECTRICITY 


Products of the Electric Furnace. Among the 
products of the electric furnace, aluminum per¬ 
haps may be ranked as the most important. This 
metal is produced by the electrolysis of a solu¬ 
tion of alumina-infused cryolite (Al 2 Na 6 Fi 2 ), to 
which other fluorides may be added. The general 
type of furnace has a large, rectangular, iron body, 
with a thick carbon lining that serves as the cath¬ 
ode. Graphite rods suspended in the bath are 
the anodes; and after an arc has been established 
between them and the carbon bottom of the fur¬ 
nace, powdered cryolite is added, and this is 
melted by the temperature of the arc. Alumina is 
then added, and the metal separates so that it 
may be removed. The oxygen liberated at the 
anode serves to oxidize the electrode. The alu¬ 
mina employed is derived from bauxite and hy¬ 
drated oxide of alumina with more or less iron; 
and if a good quality is used, an aluminum will be 
obtained that will run from 95.5 to 99.9 per cent, 
pure. 

Calcium Carbide. One of the first and most im¬ 
portant of the electrochemical products to be 
manufactured in the United States, was “ cal¬ 
cium carbide ”, useful as the basis of acetylene 
gas. This gas, as is well known, is formed by the 
action of water on the carbide and is available as 
an illuminant, or in modern industrial work, in 
connection with oxygen* for the cutting and heat 
treatment of metals. Calcium carbide is pro- 


ELECTROCHEMISTRY 


231 


duced in the electric furnace by heating lime and 
carbon together. The ordinary form of furnace 
has a carbon plate with a carbon electrode sus¬ 
pended above it, and the whole construction is sur¬ 
rounded by walls of refractory brick; but various 
other forms of furnace are used. The product is 
obtained either in the shape of an ingot from the 
hearth of the furnace, or by tapping or drawing 
off the liquid charge. In addition to being used 
for the manufacture of acetylene gas, calcium car¬ 
bide is also used in making calcium cyanamid. 
This substance is made by the reaction of nitro¬ 
gen gas on the calcium carbide, and supplies a 
material that is valuable as a fertilizer or in the 
making of synthetic ammonia. 

Carborundum. Carborundum, or silicon car¬ 
bide, is another early and important product of the 
electric furnace. It is an abrasive used for sharp¬ 
ening and polishing, in place of emery or corun¬ 
dum, which are natural substances. The method 
of manufacture is to heat coke powder to furnish 
the carbon, sand or quartz to supply the silicon, 
and common salt (to which sawdust may be added) 
to help the action. The heat of the electric arc 
tends to work the coke together, and the salt, 
acting as a flux, causes adhesion between the 
particles of the charge. The result of the chemi¬ 
cal reaction is that from the silicon oxide and the 
carbon, silicon carbide and carbon monoxide are 
formed; and the practical result, when the fur- 


232 


EVERYDAY ELECTRICITY 


nace cools, is a core surrounded by a crust of crys¬ 
tallized carborundum. Graphite is also formed by 
the decomposition of some of the carborundum. 

Artificial Graphite. Artificial graphite is used 
for lubrication, paints, dry batteries, pencils, etc., 
and is a product of the electric furnace obtained 
by heating amorphous carbon (that is, carbon not 
in the form of crystals) in the presence of ferric 
oxide or silica at a temperature so high that the 
iron or silicon is vaporized and the carbon takes 
up the crystalline form of graphite. The raw 
material employed is anthracite coal, and the 
furnace is similar to that used for carborundum. 
This process is also of interest because in the elec¬ 
tric furnace articles molded from pulverized amor¬ 
phous carbon can be “ graphitized ” without a 
change of form. 


CHAPTER XIX 


Electric Waves 

In our outline consideration of electricity we 
have discussed it as a component of the atom, in 
the form of the electron; and as a current, either 
constant, intermittent, or alternating. There is 
still another form, namely, a wave movement, 
which, consisting of rapidly recurring vibrations, 
is able to advance through both space and various 
material substances. We know that sound con¬ 
sists of a wave movement in the air, or, in fact, in 
any medium, due to vibrations of that medium. 
Light consists of a wave movement advancing at 
a rate of 186,000 miles a second. Now we find 
that there are electric waves which, spanning space 
at high velocity, make possible the radiotelegraph 
and radiotelephone, and give, in short, all the 
phenomena compressed in what is familiarly 
termed “ wireless.” We know that waves in¬ 
volve energy, or rather that energy reaches us in 
most cases in the form of waves. Heat, light, 
X-rays, all imply wave motion, just as much as do 
the waves of the ocean, though in wave length and 
frequency this motion shows a wide range of 
values. When we come to consider electric waves, 


234 


EVERYDAY ELECTRICITY 


we find we are dealing with quite the same form 
of vibration, though, as will appear, the waves are 
much longer. It should be realized that electric 
waves are produced by electricity, and are not 
electricity itself. 

As early as 1842, Joseph Henry, the illustrious 
American physicist, had discovered that the dis¬ 
charge of a Leyden jar through a coil of wire rep¬ 
resenting a resistance and an inductance, was not 
a single passage of current and did not persist in 
one direction, but occurred in an oscillatory fash¬ 
ion, surging to and fro. Other scientists, includ¬ 
ing Lord Kelvin, studied this phenomenon and 
deduced the laws governing such action. Accord¬ 
ingly, in 1865, Maxwell, utilizing these and other 
researches of Henry, and later work of Faraday, 
concluded as a result of his consideration of the 
subject that the electric oscillations resulting from 
the discharge of a Leyden jar must produce elec¬ 
tric waves that were sent forth into surrounding 
space with the velocity of light. This velocity 
had already been measured by Armand Fizeau 
(1819-1896). Waves of light were, of course, 
accepted as a part of physical theory at this time; 
but electric waves did not exist outside of Max¬ 
well’s theories and equation. 

But it did not take many years to demonstrate 
the accuracy of Maxwell’s reasoning, for it was 
discovered by Heinrich Hertz (1857-1894) in 1888 
that there were such electromagnetic waves; and 


ELECTRIC WAVES 


235 


Hertz was able to show that they were transmitted 
by nonconducting materials and reflected by con¬ 
ducting substances. His apparatus he termed an 
“ oscillator ”; and in its simple form it may 
briefly be described. 

At the spark gap of the secondary of an induc¬ 
tion coil, two rods of appreciable length, with 
plates or balls at their outer extremities and small 
balls at the spark gap, were arranged. When 



these conductors were charged by the high poten¬ 
tial current in the secondary to a certain critical 
point, where there was enough difference in the 
potential to break down the spark gap, there 
would be a discharge of electricity, which con¬ 
tinued just as in the case of the oscillating dis¬ 
charge of the Leyden jar already referred to. 

As energy is supplied by the induction coil to 
keep the two conductors charged, there is a con¬ 
tinuous oscillating discharge. The system of con- 













236 


EVERYDAY ELECTRICITY 


ductors between which it occurs is termed an elec¬ 
tric oscillator. From it are derived the electro¬ 
magnetic pulses that issue forth in the form of 
electromagnetic waves; for, of course, each oscil¬ 
lation of the current must produce a single elec¬ 
tromagnetic pulse, and with the rapid and regular 
oscillations there will pass out a series of such 
pulses as will form a train of electromagnetic 
waves. 

Although the oscillator of Hertz was very simple, 
it was fertile in its results. Straightway he found 
that in an oscillating current the period of oscilla¬ 
tion could be varied by increasing either the 
capacity or the inductance of the circuit. Thus, 
for an oscillator of small capacity and inductance, 
the frequency would be many millions a second, 
whereas for the modern powerful sources of energy 
used in commercial radio work this frequency can 
be reduced — that is, the period of oscillation in¬ 
creased — by increasing the capacity. 

Naturally, the greater the period, the longer the 
wave length. This element, so familiar in all 
radio discussion, is very important; for the longer 
the wave length, the less the energy dissipated in 
transmission. Maxwell had stated that the elec¬ 
tromagnetic wave would have the same velocity 
as light, namely, 186,000 miles (or 300,000 kilo¬ 
meters) per second. Consequently, to determine 
the wave length, we must know the frequency of 
the discharge taking place in the circuit; or con- 


ELECTRIC WAVES 


237 


versely, knowing the wave length, we can deter¬ 
mine the frequency in the same fashion. Thus, 
where X = wave length, 

V = velocity of light — 186,000 miles 
(300,000 kilometers) per second, 

F = frequency in cycles: 

V 

X = and, for a frequency of 500,000 
h 

cycles per second, 



300,000,000 meters 
500,000 


= 600 meters or 
1,968 feet. 


It may be said in passing that there are now 
direct-reading wave meters that enable us to 
determine this value in a radio circuit by a simple 
measurement. 

Detecting the Waves. So far, we have spoken 
of the electromagnetic waves as being produced in 
an oscillating circuit. We have ignored, however, 
the important matter of their recognition or detec¬ 
tion, or even how it is known that the stream of 
sparks between two conductors of an induction 
coil was even producing electromagnetic waves 
or waves of any kind. 

It must be recalled that when a conductor is cut 
by a magnetic field, there will be produced in that 
conductor an electromotive force. Consequently, 
if the magnetic field is oscillating, due to oscillat¬ 
ing discharges, then naturally the electromotive 
force set up will also be oscillating. Now, if we 




238 


EVERYDAY ELECTRICITY 


take a conductor in the form of a loop of wire, 
with a minute spark gap, then when the oscillating 
current flows there will be a discharge across this 
gap if the potential difference is high enough. 
This was the first wave detector, and it was used 
by Hertz to detect his electric waves. Placing his 
loop at some distance from the source of waves, 
he noted at the gap, possibly by the use of a micro¬ 
scope or magnifying glass, the spark produced. 
It was found that the sensitiveness of a detector 
could be increased by adjusting its capacity and 
inductance so that its natural frequency for elec¬ 
tric oscillation could correspond with the fre¬ 
quency of the incident electromagnetic waves. 

Although the oscillator of Hertz served to prove 
the existence of electromagnetic waves by actually 
producing them, even if they were but a few 
meters in length, yet both it and his detector were 
far removed from a scale in which they could be 
available for any practical use. They could not, 
for example, be employed in the sending of signals, 
an idea that occurred to various experimenters 
who were studying the waves with much the same 
form of apparatus as was used by Hertz. 

It was necessary to increase the potential differ¬ 
ences in the oscillating circuit and also its capac¬ 
ity; and by the time wireless telegraphy was 
developed, it was found that by using an alter¬ 
nating-current generator in series with the primary 
coil of a step-up transformer it was possible to 


ELECTRIC WAVES 


239 


develop a sufficiently high potential and a suffi¬ 
cient amount of energy. In such an arrangement, 
a spark gap was placed in the secondary-coil cir¬ 
cuit, and also the primary coil of a transformer 
whose secondary was connected with the antennae. 
Across the circuit near the spark gap is a con¬ 
denser, and in the original circuit at the generator 
there is a key to open and close the circuit for the 


Tra/is/n/ffiA? 

/1/tfenna, 



ffecejr/W# 

/Ju/eona. 


: dor/aJde 
Condenser 



Ground 


Fig. 81: The Radiotelegraph. — Diagram showing transmitting and 

receiving stations. 


purpose of transmitting signals in the form of 
waves sent out from the antennae. 

The first actually to transmit signals by electric 
waves on a commercial basis was Guglielmo Mar¬ 
coni, who was able to utilize much of the work 
done previously by other scientists and at the same 
time to carry on extensive experiments of his own. 
He developed the device for receiving the waves 
and improved the methods of propagating them, so 























240 


EVERYDAY ELECTRICITY 


that he was able to demonstrate conclusively that 
radiotelegraphy was distinctly practicable. Natu¬ 
rally, other experimenters soon entered this field. 
The range of transmission was increased and more 
sensitive devices were developed for the detection 
of the waves. The various properties of the waves 
also were studied, and different forms of generators 
were used until trans-Atlantic communication was 
established. With radiotelegraphy an assured 
fact, the next work was the radiotelephone. The 
various vacuum-tube detectors that had been 
used with the radiotelegraph were found particu¬ 
larly adaptable for the waves sent out from radio¬ 
telephone transmission stations. But almost at 
a bound the radiotelephone came into general use 
and broadcasting stations sent out the news of 
the day, music, lectures, and various interesting 
information. 

In fact, radiotelegraphy and radiotelephony be¬ 
came an important field of science and application 
almost simultaneously, and the study of the waves 
was undertaken with this end in view. So gen¬ 
erally has this been carried on and so special is the 
interest in the subject that proper space to permit 
of adequate treatment cannot be given in a general 
volume on electricity* Accordingly, the reader is 
referred to an interesting and comprehensive trea¬ 
tise in this series, prepared by John V. L. Hogan 
and entitled “ The Outline of Radio.” 


CHAPTER XX 

X-Rays 


For the production of X-rays there is required a 
vacuum tube — that is, a glass container from 
which the air has been exhausted to a high degree 
and which has metallic electrodes sealed into the 
glass to afford a 
path for the cur¬ 
rent. The positive 
pole is known as 
the anode, its con¬ 
ductor coming 
from the positive 
terminal of a bat¬ 
tery, induction 
coil, or generator, 
from which is 
supplied sufficient 
voltage to force the current across the interval 
between it and the negative pole, known as the 
cathode. When such a current is passed, it will 
be found that from the cathode is emitted a beam 
of rays impinging on the surface of the glass 
directly opposite and causing it to fluoresce or 
glow with a greenish hue. 



Fig. 82 : High-vacuum tube of Crookes, 
with cross of mica in the path of the cathode 
rays and producing a shadow at the larger end 
of the tube. The cathode is indicated at K. 
Either of the terminals sealed into the glass at 
A and B serves as the anode. Cathode rays 
are emitted in a direction normal to the cathode 
plate. 









242 


EVERYDAY ELECTRICITY 


These cathode rays, as may have been inferred, 
are made up of electrons, which, as we know by 
this time, are minute bodies, lighter than the hy¬ 
drogen atom by nearly two thousand times, and 
moving with a higher velocity — under average 
conditions approximately 20,000 miles a second 
or about one tenth the velocity of light. Among 
the peculiarities possessed by these cathode rays, 
in addition to their causing fluorescence of the 
glass, is that they are deflected by the action of a 
magnet; and this led to the conclusion that they 
carried electric charges, which was indeed the 
case. Professor (now Sir) J. J. Thomson meas¬ 
ured the amount of such deflection. With a 
knowledge of the electrical force involved, and with 
a known intensity of magnetism, he found that by 
observing the deflection he was able to determine 
the mass and, therefore, the size of the electron. 
This was done in one of the most brilliant experi¬ 
ments recorded in the annals of physics, the re¬ 
sults of which were clearly to establish the exist¬ 
ence and size of the electrons. 

When the cathode rays strike against the op¬ 
posite electrode, or a solid plate termed the “ anti¬ 
cathode ”, there are produced what are known as 
the X-rays, with which to-day our dentists at 
least have made us familiar. If we look at the 
diagram of the vacuum tube (Figure 82), the pro¬ 
duction of X-rays at the “ anticathode ” will be 
evident. These X-rays (as Professor W. K. 


X-RAYS 


243 


Roentgen found when, in 1895, he discovered 
their nature and effects) have a power of pene¬ 
tration that enables them to go through objects 
that in our more ordinary experience are con¬ 
sidered opaque. Thus, the X-rays are absorbed 
by glass and metals, notably lead, but they are 
transmitted very freely by aluminum, wood, flesh, 
and other media. Roughly speaking, the trans¬ 
parency of any substance to X-rays is in most 
cases inversely proportional to the specific gravity 
of that substance. For example, the transpar¬ 
ency of zinc is low, being 0.055, whereas that of 
water is taken as 1.00; of aluminum, 0.38; of 
bone, 0.56; of cardboard, 0.80; of rubber, 1.10; 
and of pine wood, 2.21. Lead, which is used as 
a protective screen in most X-ray installations, 
has a transparency of only 0.055 on the same basis 
on which iron has one of 0.101; silver, of 0.70; 
and gold, of 0.030. 

The power of any substance to absorb X-rays 
depends not only upon the nature of the substance, 
but also on the quality of the rays emitted from 
the tube. These rays indicate their presence by 
causing a surface coated with barium platino- 
cyanide to glow or fluoresce; and if we interpose 
in their path an object of metal (or, let us say, of 
bone — some substance that is less transparent), 
there will be a distinct shadow formed on the flu¬ 
orescent screen. If a photographic plate is sub¬ 
stituted for the fluorescent screen, it will be af- 


244 


EVERYDAY ELECTRICITY 


fected by the rays as by ordinary light, but any 
part where an X-ray shadow is cast will be less 
affected and will remain light against a dark back¬ 
ground when the plate is developed. Conse¬ 
quently, the density of the absorbing substance is 
measured by the relative intensity of the action 
on the photographic plate. 

The usual form of apparatus is a so-called 
“ focus tube ”, in which a high unidirectional 
electromotive force is used. The anode and 

cathode, which, with 
the other parts, are in¬ 
dicated in the diagram 
(Figure 83), are made 
of aluminum on ac¬ 
count of the low rate 
of disintegration of this 
metal, and are con¬ 
nected with the wires 
sealed into the bulb. The anticathode is gener¬ 
ally of platinum in order to withstand the intense 
heat produced by the bombardment of the elec¬ 
trons sent out from the cathode. 

The cathode is usually made concave spheri¬ 
cally, so as to focus the cathode rays on the sur¬ 
face of the anticathode, which often is electrically 
connected with the anode to prevent the possible 
emanation of the cathode rays at the anode sur¬ 
face. The tube itself is made of thin glass, to 
reduce the absorption of the X-rays. 



Fig. 83: Cross Section of an X-Ray 
Focus Tube. 












1,000-Kilowatt Vacuum Tube in the Research Laboratory of the 
General Electric Company at Schenectady, N. Y. 



Courtesy of the General Electric Company. 
Coolidge Radiator X-Ray Tube. 


VACUUM TUBES 























X-RAYS 


245 


An essential of the vacuum tube is that it should 
contain a high degree of exhaustion, but the vac¬ 
uum must not be too nearly perfect; and there 
have been developed self-acting X-ray tubes that 
regulate the vacuum. There are also so-called 
44 regenerative tubes ”, containing palladium, 
which at ordinary temperature occludes gas and 
under heat gives it off, thus maintaining within 
the tube a constant pressure. 

Penetration of X-ray Bulbs. The penetrating 
power of an X-ray bulb depends, within certain 
limits, upon its vacuity, and on this basis tubes 
are classified. The so-called 44 hard ” tube is a 
high-vacuum tube that emits a few rays of great 
penetrating power, whereas the 44 soft ” tube has 
a low vacuum and gives off a great number of rays 
of less penetration. To obtain the greatest 
amount of contrast upon the photographic plate 
or fluorescent screen, it is preferable to employ a 
soft tube rather than a hard tube, as the rays from 
a hard tube may be transmitted with nearly equal 
strength through all the constituent parts of the 
object and not afford the significant gradations of 
tone desirable in anatomical and other studies. 

The Coolidge Tube. The most efficient vac¬ 
uum tube thus far developed has been the Cool¬ 
idge tube, which not only has a higher vacuum but 
also, by the use of an external circuit and a wire 
grid kept at a high temperature, raises the temper¬ 
ature of the cathode so that a greater number of 


246 


EVERYDAY ELECTRICITY 


electrons are emitted. By varying the current, 
and consequently the temperature, the velocity of 
the electrons may be varied. One result of such 
variation is that with a great velocity given to the 
electrons, hard rays are produced and are likely to 
be thus characteristic of the metal of the target. 



Fia. 84 : Cross Section of the Coolidge X-Ray Tube. 

On the other hand, with a less velocity, the re¬ 
sulting rays are soft. 

X-rays in Medicine and Surgery. The early 
discovery that flesh, bone, and other parts of the 
human body varied in their transparency to the 
X-rays, as was shown by the shadow of the bones 
of the hand on a fluorescent screen, was applied to 
medicine and surgery. Many discoveries of im¬ 
portance in apparatus and technique have followed, 
so that now the X-rays are available for diagnosis 
not only in such cases as fractures but through a 


























X-RAYS 


247 


wide range of surgical and medical conditions. 
Furthermore, the rays themselves were found to 
possess certain physiological effects; and from the 
time of the early X-ray burns, their activity in 
this direction has been studied. To-day the X- 
rays are applied for various skin diseases, such as 
lupus, eczema, syphilitic lesions, naevus, sycosis, 
favus, acne, and psoriasis. Extensive use has been 
made of the X-ray in the treatment of cancer, 
including carcinoma, epithelioma, and sarcoma. 

The first work done in this field was the surgi¬ 
cal study of bones and their diseases, especially 
joints, in addition to the more ordinary cases of 
fracture, in which it was desired to determine 
(a) whether a fracture existed and (6) the progress 
that was being made in the setting of the parts. 
Also, the X-rays were employed to detect the pres¬ 
ence of foreign bodies whose removal might re¬ 
quire surgical treatment. In the case of a frac¬ 
ture, two or more views are always taken to avoid 
any error, and the surgeon, as well as the X-ray 
operator, soon acquires a proficiency in interpret¬ 
ing the photographs. The use of the X-ray is 
essential in military surgery; and in war, portable 
outfits are carried even to the advance hospitals, 
so that a correct diagnosis can be made at the 
earliest possible moment. 

The X-rays are also used for the detection of 
gallstones or calculi, as these bodies stand out in 
clear relief in the picture. With this aid, the 


248 


EVERYDAY ELECTRICITY 


treatment may be carried on with intelligence. 
Also, the progress of the art has made X-rays 
especially useful in dental surgery in detecting the 
condition of the teeth, roots, and sockets; and in 
diseased condition of the jaw. 

In general, by diagnosis the X-ray can detect 
the presence and extent of tuberculosis, pneu¬ 
monia, pleurisy, hydrothorax, and empyema, so 
that the progress of these ailments can be observed, 
and their cure carried on, with a fuller knowledge 
of the internal condition than ever before. Like¬ 
wise, it is possible to study the presence of any 
new growth, and also the movements of the heart 
and its displacement, or the displacement of other 
organs. 

The X-rays have been particularly useful in de¬ 
tecting various conditions of the stomach. By 
the administering of large doses of bismuth in so¬ 
lution, the stomach is filled with a fluid quite 
opaque to the rays; so that when a photograph 
is made, it is possible to detect any abnormal con¬ 
ditions. Furthermore, by the use of X-rays, pic¬ 
tures of various portions of the digestive tract can 
be taken; this being made possible by the new 
tubes, which cut down the time of exposure and 
produce sharp and clear shadows. 

As regards the therapeutic effect of the X-rays, 
certain great and unmistakable advantages have 
been claimed. A promising field has been opened 
up, which seems likely to be extended as more 


X-RAYS 


249 


powerful and more exactly controlled apparatus 
is placed in the hands of the physicians. Thus, 
hopes are entertained for the amelioration of can¬ 
cer by the use of X-ray bulbs supplied with elec¬ 
tricity of a very high potential and subject to ac¬ 
curate control. In some cases, by the use of these 
X-rays, as well as with simpler equipment, bene¬ 
ficial results have been obtained; but the matter 
has not advanced beyond the experimental stage, 
and X-ray therapeutics, like the use of radium, 
enjoy rather a promising future than an assured 
and recognized field of wide present-day useful¬ 
ness. 


CHAPTER XXI 


Lightning 

When Benjamin Franklin, as early as 1750, con¬ 
jectured the identity of the lightning flash with 
electricity, he naturally was not able to explain 
this external natural phenomenon. Of course, he 
appreciated the fact that the thundercloud was 
charged with electricity; and in later experiments, 
in 1753, he found that by means of a pointed iron 
rod on a housetop he could discharge the electricity 
harmlessly and thus prevent a sudden and unex¬ 
pected flash, with its possibly disastrous results. 

In the case of the thundercloud, however, we 
are dealing with a charge on a different substance 
from the solids that we hitherto have considered. 
Ordinarily, a solid or a liquid is not charged 
throughout its volume, but merely on the surface. 
If we have a gas or a vapor, on the other hand, we 
are dealing with an aggregation of separate par¬ 
ticles, each one of which can receive an individual 
charge. For example, the air in a room where an 
electric machine or other generator of high-tension 
current is in operation will receive a charge. 

In the same way, a cloud, which is composed of a 
large number of minute particles of water, dust. 


LIGHTNING 


251 


and other materials, may become charged, due to 
the fact that these individual particles are them¬ 
selves charged. The particles of moisture may 
be derived from evaporation at the earth’s sur¬ 
face, and each particle may have its separate 
charge. If these particles unite, the charge, of 
course, increases and the electric potential will be 
greater. A cloud, accordingly, may be formed of 
a large number of these charged particles; and as 
the drops coalesce, the potential may become 
higher, and the lower portion of the cloud will 
experience a constantly greater electrification. 

Under such conditions, it will be manifest that 
the surface of the earth below will act as a plate of 
a condenser, and condensed electricity of the op¬ 
posite character will be brought to its surface, 
that of the same kind as the electrification of the 
cloud being repelled. The intervening air serves 
as the dielectric or an insulator. As the potential 
of the cloud increases, a point is finally reached at 
which the strata of air, unable to resist the strain, 
give way, with the result that there is the bright 
and familiar lightning flash. This huge spark may 
be more than a mile in length, and its passage may 
give rise to new distributions of charges and ag¬ 
glomerations of particles within the cloud. This 
will appear to the observer of a thundercloud, 
which usually is a flat-bottomed mass of cloud at 
the top of which there is a continual movement. 

The lightning spark also accounts for the sound 


i 


252 


EVERYDAY ELECTRICITY 


of the thunder; for, as it passes, it heats the sur¬ 
rounding air and vapor to a high temperature and 
gives rise to a sudden violent expansion and com¬ 
pression, with the production of a partial vacuum. 
There is thereupon a sudden rush of air into the 
partial vacuum, resulting in the production of 
sound. The nature of this sound varies, as we 
know, from the short, sharp thunderclap, due to 
a straight and short spark, to the rattle following 
a spark whose path is long and not straight. The 
rolling or rumbling is due to the echoes from other 
clouds, and may be heard for a considerable space 
of time after the disappearance of the lightning 
spark responsible for the disturbance. 

It is well known that flashes of lightning are 
over a mile long in many cases; and it has been 
estimated that the potential required to cause such 
a flash would be 5,000,000,000 volts — this esti¬ 
mate being based on the breakdown voltage of 
air, which is about 30,000 volts per centimeter. 
Such a statement is a pure hypothesis, as it has 
been suggested from the experience of experi¬ 
menters with voltages exceeding a million that with 
long air gaps, and with extremely high potentials, 
there may be different properties in the air from 
those ordinarily realized and assumed. 

Lightning Protection. The disastrous results of 
lightning long have been appreciated, and Frank¬ 
lin’s experiments were undertaken to devise some 
means to decrease them. After performing his 


LIGHTNING 


253 


famous kite experiment in June, 1752, he erected 
on his house in Philadelphia, in the summer of the 
following year, a rod of iron with a short point 
seven or eight feet above the roof, the rod itself 
extending five feet into the ground. This device 
was installed both as a protective measure and 
to afford opportunity for observing the effects 
of atmospheric electricity. Franklin was able in 
addition to persuade several of his friends to mount 
lightning rods on their respective houses; and after 
patient waiting for a few months, during a severe 
thunderstorm, the rod on the home of a Mr. West 
was duly struck. The flash was carried off with¬ 
out damage to the building, and the only evidences 
were a melting of the rod at its point and some 
slight disturbances of the earth where the iron en¬ 
tered the ground. 

Lightning rods gradually were accepted in 
Europe, and both in America and abroad Franklin 
was regarded as an infidel for attempting to inter¬ 
fere with the operations of Divine Providence. For 
this reason the use of lightning rods on churches 
lagged considerably behind their applications to 
other edifices. The Senate of Venice on May 9, 
1778, ordered the erection of lightning rods 
throughout the republic, and this was the first 
governmental recognition of Franklin’s discovery. 

From such beginnings, the use of the light¬ 
ning rod became general and its efficiency was 
demonstrated on many occasions. Nevertheless, 


254 


EVERYDAY ELECTRICITY 


there has been and is a wide divergence of popular 
opinion, not only as to the merits of lightning-rod 
installations, but also as to the best methods of 
installation. In fact, one can hardly pick up any 
work on this subject without finding record of sub¬ 
stantial disagreement between various authorities. 
For example, in some cases iron is advocated for 
conductors, whereas in others copper is recom¬ 
mended on account of its high conductivity. 

There is also wide divergence of opinion as to 
the shape and size of the conductor, and as to the 
actual methods of protection in the distribution 
of points and conductors. This ranges from the 
scientific side to the commercial; and, as might 
be expected, there is a striking lack of harmony in 
the methods followed and devices offered for sale 
by commercial firms. At the same time, there is 
thought to be in the United States a surprising 
lack of protection against lightning; it having 
been estimated that not more than 15 or 20 per 
cent, of the buildings liable to damage by light¬ 
ning are in any way protected against it. 

The lightning rod in the United States was 
brought to serious discredit in the last century by 
unscrupulous swindlers, who traveled through the 
country victimizing the farmers with more or less 
success. As a result of such pernicious activity, 
it has taken some years to restore confidence in 
this protective device; and there has also been the 
lack of harmony, already referred to, on the part 


LIGHTNING 


255 


both of scientific men and of those interested in the 
commercial sale and installation of such equip¬ 
ment. It is now believed that even a defective 
lightning rod is better than no rod at all, and that 





Gw/idtirfo/K/i/efor 

Fig 85 : Roof plan of a rectangular barn with shingle roof, showing the 
course of lightning rods and the location of air terminals. (From U. S. Bureau 
of Standards, “Safety for the Household.”) 

the resistance of the conductor is of little impor¬ 
tance, the connections being the leading considera¬ 
tion. The surface of a lightning conductor is 
also considered as important as its cross section, 
and its self-induction should be kept as small as 
possible. 

The chief source of danger to a protected build¬ 
ing is usually in the form of any considerable mass 
























256 


EVERYDAY ELECTRICITY 


of metal in close proximity to the lightning rod 
and not connected to it. Instances of such metal 
masses would be sheet-metal roofs, valleys, orna¬ 
ments, gas and water pipes, electric circuits, and 
other more or less insulated metallic bodies. 



Fig. 86 : Roof plan of a house, showing an installation of lightning rods, with 
connections to gutters and valleys, and ground connections for down spouts. 
(From U. S. Bureau of Standards, “ Safety for the Household.”) 


These should be connected in some way to the 
lightning-rod system, as, should they become a 
path for the lightning stroke, damage to the non- 
metallic portions of such path is likely to ensue. 

In the United States, it is usual to provide 



























LIGHTNING 


257 


lightning rods with points; in Europe, there has 
been employed a so-called “ contour system ”, 
by which iron wires or sheet-iron bands are laid 
on the conductors of the roof, forming a network. 
This system has b en used in Hungary, and was 
recommended for use in Holland. One of the 
developments of the installations of lightning rods 
on buildings has been the pronounced tendency to 
do away with the use of insulators of glass or 
porcelain in the clamps fastening the rods to the 
buildings. Inasmuch as the purpose of the light¬ 
ning rod is to collect and dissipate electrical en¬ 
ergy with as little disturbance to the surrounding 
material as possible, it is necessary that all the 
metallic parts of the building should be connected 
with the rod; and the use of glass and porcelain 
in the clamps only serves to make the mechani¬ 
cal construction less secure. Moreover, if the ex¬ 
terior of a building is damp from rain or other 
cause, the electric charge may be spread well over 
its surface; and if this charge has difficulty of 
access to the rod it may develop a spark at the 
insulators, due to leakage. 






GLOSSARY 


Accumulator. A secondary (or storage) cell or bat¬ 
tery. See Battery, Storage. 

Alternating Current. An electric current of which 
the direction is reversed at regularly recurring 
intervals. Ordinarily, the term “alternating cur¬ 
rent” refers to the periodically varying current, 
with successive half-waves of the same shape and 
form; the shape or form being obtained by plotting 
the instantaneous values of the current in a curve 
in which tirr is expressed in rectangular coor¬ 
dinates. 

Alternator. A synchronous generator for alter¬ 
nating current, either single-phase or polyphase. 
See Alternating Current ; Generator. 

Ammeter. A Galvanometer ( q.v .), or electrodyna¬ 
mometer, direct-reading in amperes and of rugged 
construction, for measuring current strength. 

Ampere, International. The practical unit of cur¬ 
rent; one tenth of the unit of current in the ab¬ 
solute system of electromagnetic units; legally 
defined as the current that, under standard condi¬ 
tions, in passing through a solution of nitrate of 
silver, would deposit silver at the rate of 0.001118 
gram per second. 

Ampere-hour Meter. A measuring device to read 
directly the quantity of electricity passing through 


260 


EVERYDAY ELECTRICITY 


a circuit. Such meters are divided into electro¬ 
lytic and electromagnetic (or motor) meters. 

Ampere-turns. The product of the current intensity 
and the number of turns in a spiral conductor. 
In such a conductor, the total magnetizing force 
is proportional to the number of ampere-turns. 

Anion. The group of ions, or constituents of an 
Electrolyte (q.v.) liberated at the anode, or elec¬ 
trode connected to the positive pole of the conduc¬ 
tor. See Anode ; Ion. 

Anode. (1) The conductor by which the electric cur¬ 
rent enters an electrolyte or some electrical de¬ 
vice. It is connected with the positive terminal of 
the generator. (2) The electrode toward which 
the electrons flow. (3) A positively charged elec¬ 
trode. See Cathode. 

Antenna. A system of conductors for radiating or 
absorbing energy of electromagnetic waves used 
in radio communication. 

Arc. An electric flame or discharge established be¬ 
tween the terminals of a conductor in a circuit 
after contact has been established and then broken. 

Armature. (1) A piece of soft iron placed across the 
poles of a horseshoe magnet and accordingly mag¬ 
netized by induction. (2) The moving coils of 
wire rotated between the poles of a Generator 
or Motor ( qq.v .). 

Arrester, Lightning. A Spark Gap ( q.v ), or other de¬ 
vice designed to protect electric lines from abnormal 
increase of voltage due to lightning discharge or 
from electric oscillations caused by switching loads 
on or off in contact with high-voltage circuits. 


GLOSSARY 


261 


Battery. A group of voltaic or storage cells elec¬ 
trically connected. 

Battery, Primary. Two or more voltaic cells so 
connected as to afford increased current or Elec¬ 
tromotive Force ( q.v .). See Cell, Primary. 

Battery, Storage. Two or more secondary cells or 
accumulators connected to afford increased cur¬ 
rent or Electromotive Force (q.v.). 

Booster. A generator inserted in series in a circuit 
to raise the voltage. It may be driven by an elec¬ 
tric motor or otherwise. 

British Thermal Unit. The heat-energy developed 
from the combustion of unit mass or weight of a 
fuel. The B. T. U. is equal to 777.5 foot pounds, 
and is the heat required to raise one pound of 
water through one degree Fahrenheit. 

Brush. In a generator or motor, one of the fixed con¬ 
tact pieces whereby the current is led from, or to, 
the commutator. 

Bus-bar. The common circuits to which the genera¬ 
tors of a power plant are connected, and from 
which the feeder mains derive their energy. 
Such structures are massive and of high con¬ 
ductivity, and are connected with the switch¬ 
board. See Feeders. 

Candle Power. Luminous intensity expressed in 
candles; the international candle being a unit 
derived from international agreement between 
the three national standardized laboratories of 
France, Great Britain, and the United States, and 
maintained by means of standard incandescent 
lamps. 


262 


EVERYDAY ELECTRICITY 


Capacitance (or Capacity). (1) The ratio of the 
charge in a conductor to its potential; usually 
measured by means of a unit known as the farad. 
(2) The quality permitting the storage of an elec¬ 
tric charge in a condenser. See Charge; Con¬ 
denser; Farad. 

Capacity. See Capacitance. 

Cathode. (1) The electrode by which the current 
leaves an electrolyte or a vacuum tube. (2) The 
electrode from which the electrons flow. (3) A 
negatively charged electrode. See Anode. 

Cathode Ray. A stream of electrons set into rapid 
motion by an electric field of force, as in a vacuum 
tube. See X-rays. 

Cation. One of the positively charged ions developed 
upon ionization of a solution. These ions are liber¬ 
ated at the cathode or electrode connected to the 
negative terminal of the conductor. See Cathode. 

Cell. A single voltaic element, with electrolyte and 
container. 

Cell, Primary. A unit consisting of a combination 
of two elements placed in an electrolyte, and capa¬ 
ble of producing a continuous current and trans¬ 
forming chemical into mechanical energy. 

Charge. The quantity of electricity residing on a 
surface, or the preponderance of electrons of the 
same kind in a body. 

Chemical Equivalent. The relative mass of an Ion 
(< q.v .) divided by the number of charges carried by 
the ion; or in chemistry, the ratio of the atomic 
mass to the valence ( i.e ., the degree of power of an 
atom to combine with other atoms). 


GLOSSARY 


263 


Circuit Breaker. A device to open, by some form 
of latch or other mechanism, an electric circuit 
normally held closed. It may be either automatic, 
manual, or ‘"remote controlled/’ 

Coherer. A detector of electric oscillations, consist¬ 
ing of a glass tube containing a mixture of metal¬ 
lic filings whose conductivity changes under the 
influence of electric waves used in radioteleg¬ 
raphy. See Oscillations. 

Commutator. In a direct-current generator, a device 
consisting of (a) insulated segments of a cylinder 
to which the coils of the rotating armature are 
joined, and (6) with respect to the external circuit, 
brushes to collect the current, whose direction is 
thus changed each time the direction of the electro¬ 
motive force in the conductor is reversed. 

Compound-wound. Having duplex windings. The 
term is applied to a direct-current generator or 
motor in which the field magnets are excited by 
both shunt and series windings. 

Condenser. A system consisting of two conductors 
insulated one from the other and designed to store 
an electric charge. Its capacity is measured in 
farads. See Farad. 

Conductance. The inverse of Resistance ( q.v .); the 
property of a conductor permitting the flow of an 
electric current. 

Conductivity. The specific conductance of a vol¬ 
ume of unit length and cross section. 

Conductor. A wire, or a combination of wires not 
insulated one from another, suitable for carrying a 
single electric current. 


264 


EVERYDAY ELECTRICITY 


Conduit. A pipe or tube for containing electric wires 
or cables. 

Contactor. A device for repeatedly making and 
breaking an electric circuit under normal con¬ 
ditions. 

Continuous Current. A nonpulsating direct cur¬ 
rent. See Direct Current. 

Controller. A device for regulating the current or 
voltage of an electric circuit. 

Converter. A machine employing mechanical ro¬ 
tation in changing electrical energy from one form 
into another; there being direct-current convert¬ 
ers, synchronous converters, cascade converters, 
frequency converters, and rotary phase converters. 

Coulomb. The electrical unit of quantity; the quan¬ 
tity of electricity transferred by a current of one 
ampere in one second. 

Current. The flow of electricity, or passage of elec¬ 
trons, between two points having a difference of 
voltage. 

Cycle. One complete set of positive and negative 
values of an alternating current. Expressed some¬ 
what differently, in an alternating current, the 
time required for the current to pass through one 
cycle is that of a complete set of positive and 
negative values. See Period. 

Detector. In radio communication, a device to trans¬ 
form the electrical oscillations set up in a receiv¬ 
ing system into visible or audible indications. 

Diamagnetic Substance. A substance that is re¬ 
pelled by a magnetic pole and that tends to arrange 
itself perpendicularly to the magnetic lines of force. 


GLOSSARY 


265 


Dielectric. A nonconductor used as an insulator 
to separate the plates of a condenser. 

Direct Current. An electric current flowing in 
one direction between two points having a differ¬ 
ence of potential. Ordinarily the term refers to a 
practically nonpulsating current, also known as 
continuous or unidirectional current. 

Dynamotor. A transforming device in which, in one 
machine with a single magnetic field, both motor 
and generator action are combined; either with 
two armatures or with one armature having two 
separate windings and independent commutators. 
See Armature ; Commutator. 

Eddy Current. A current circulating wholly within 
a plate or other metal moving in a magnetic field. 

Efficiency. In an electric machine or apparatus, the 
ratio of its useful output to its total input. 

Electrolysis. The separation of the different ions 
in an Electrolyte ( q.v .), one from another. 

Electrolyte. A liquid containing ions. See Ion. 

Electromagnet. A core of iron or steel magnetized 
by the passage of an electric current through a 
surrounding coil of wire. 

Electrometer. An instrument for measuring dif¬ 
ferences of electric potential, usually by the amount 
of attraction or repulsion of two charged sur¬ 
faces. 

Electromotive Force. The property tending to set 
electricity into motion through energy obtained 
from a transformation of some other sort of energy. 

Electron. A minute, negatively charged particle of 
matter. 


266 


EVERYDAY ELECTRICITY 


Electrostatics. The study of the manifestations of 
electricity at rest. 

Energy. The ability to do work; measured in elec¬ 
tricity by the joule. Electrical energy may be 
transformed into mechanical or other energy, and 
vice versa. See Electromotive Force; Joule. 

Exchange, Telephone. One or more central offices, 
with associated plant, for the maintenance of 
telephone service in a local community. 

Exciter. Some form of direct-current generator em¬ 
ployed to energize the field magnets of an alter¬ 
nating-current generator. 

Farad. The practical unit of electrical capacitance; 
the capacitance of a condenser charged to a poten¬ 
tial of one volt by one coulomb. See Condenser. 

Feeders. A system of conductors run from the power 
house to distribution centers or feeding points. 

Field. (1) A region in which a force would act upon 
a magnetic pole, if such a pole were placed there, 
is called a magnetic field of force. (2) A region in 
which an electric charge experiences a force is 
called an electric field of force. 

Flux. (1) Radiant flux is the ratio of flow of radiation 
with reference to energy expressed in ergs per sec¬ 
ond or watts. (2) Luminous flux is determined 
with reference to the visual sensation, and signifies 
the whole beam of light from a given source. The 
unit of luminous flux is called the Lumen ( q . v .). 

Flux Density. The amount of magnetism per unit 
of surface. 

Flux, Magnetic. An effect created by magneto¬ 
motive force in a magnetic circuit, just as electric 


GLOSSARY 


267 


current is an effect created by electromotive force 
in an electric circuit. It varies directly as the 
magnetomotive force and inversely as a quality 
of the magnetic circuit known as “reluctance”, 
which corresponds to the “resistance” of an elec¬ 
tric circuit. See Oersted. 

Foot Candle. A practical unit of illumination, equal 
to one lumen per square foot. See Lumen. 

Force. That which changes, or tends to change, the 
motion of one body with respect to another. 

Frequency. In an alternating current, the number 
of cycles through which it passes per second, or 
the reciprocal of the Period ( q.v .). 

Galvanometer. A device for measuring or detecting 
an electric current; usually by the action of a 
current (a) in a coil on a suspended magnetic 
needle or (6) in a coil suspended in a magnetic 
field. 

Gauss. The unit of intensity of a magnetic field, 
equivalent to one dyne per unit pole; a dyne being 
(in the centimeter-gram-second system) the force 
that, acting on a gram for one second, generates 
a velocity of one centimeter per second. 

Generator. A machine that transforms mechanical 
energy into electrical energy. 

Ground. The connection that a conductor makes with 
the earth. 

Henry. The unit of self-induction or inductance; 
the inductance in a circuit when the electromotive 
force induced in the circuit is one volt while the in¬ 
ducing current varies at the rate of one ampere a 
second. 


268 


EVERYDAY ELECTRICITY 


Hertzian Waves. Electromagnetic waves in the 
ether, produced by high-frequency oscillations. 
See Waves, Electromagnetic. 

High-frequency Currents. Alternating currents 
of 1,000 or more cycles per second, flowing mainly 
along the outer surface of the conducting wire. 
See Cycle. 

Horsepower. A unit of power equal to 550 foot 
pounds per second, or 0.7457 kilowatts. 

Hysteresis. In magnetism, the lagging of the induc¬ 
tion density behind the change in the magnetizing 
field producing it. 

Impedance. The resistance to the passage of an al¬ 
ternating current, due to the development of a 
counter electromotive force in a circuit with 
Self-induction ( q.v ). Impedance in a circuit 
reduces an alternating current. See Alternat¬ 
ing Current; Electromotive Force. 

Inductance. The property possessed by a circuit 
of storing up energy. It prevents the instant es¬ 
tablishment or destruction of a strong electric 
current in such a circuit. 

Induction. (1) The communication of magnetism 
from one body to another without actual contact. 
Also (2) the action of a charged body to develop 
electrification in an adjoining conductor without 
contact; and (3) the change in a current produced 
by a change in speed of an electron moving across 
a varying magnetic field. 

Induction Coil. An arrangement of two coils, a 
primary and a secondary, with some form of in¬ 
terrupting device (and usually a condenser), 


GLOSSARY 


269 


to transform a low-voltage direct current into an 
alternating or unidirectional intermittent of high 
electromotive force. See Direct Current. 

Induction Motor. An alternating-current motor, 
either single-phase or polyphase, comprising in¬ 
dependent primary and secondary windings, one 
of which (usually the secondary) is on the rotating 
member. The secondary winding receives power 
from the primary by electromagnetic induction. 
See Induction. 

Inductor-alternator. An alternator in which both 
field coils and armature are stationary and iron 
cores or inductors, by moving past the coils, alter 
the magnetic flux through them. 

Insulating Material (or Insulator). Material of 
such high resistance that it can be used as a non¬ 
conductor of electricity. 

Insulation. The use of nonconducting material to 
prevent the flow or escape of current. 

Ion. An electrically charged particle resulting when 
a molecule is separated into its constituent ele¬ 
ments. 

Ionization. The process of separating a molecule 
into its. ions. 

Joule. An electrical unit of work, practically equiv¬ 
alent to the energy expended in one second in main¬ 
taining a current of one ampere against a resist¬ 
ance of one ohm. 

Kilo. A prefix for units indicating 1,000; for example, 
kilowatt = 1,000 watts, kilogram= 1,000 grams, etc. 

Kilowatt. A practical unit of power equal to 1,000 
watts and to 1.341 horsepower. See Watt. 


270 


EVERYDAY ELECTRICITY 


Lightning Arrester. A device for protecting cir¬ 
cuits and apparatus against lightning or other 
abnormal high-voltage risks of short duration. 

Lightning Protection. A device consisting of a 
spark-gap impedance coil, or a conductor connected 
with the ground, used in connection with a circuit, 
machine, or building. 

Loaded Line. A telephone line in which the normal 
reactance of the circuit has been altered for the 
purpose of increasing its transmission efficiency. 

Local Action. In a primary cell, the formation of 
local or parasitic currents at the zinc plate, due to 
impurities. It may be reduced by amalgamating 
the zinc. 

Lumen. The unit of luminous flux; equal to the flux 
emitted in a unit solid angle by a uniform point 
source of one international candle. See Flux. 

Magnet. A natural ore, or artificially prepared piece 
of iron or steel, capable of attracting iron and 
steel and exhibiting polarity. 

Magneto-machine. A mechanical device for pro¬ 
ducing an electric current by rotating a conduc¬ 
tor in a magnetic field. 

Magnetomotive Force. In a coil or other mag¬ 
netic system, the measure of the work done on a 
unit pole in moving it once around the closed 
path, or 1.257 times the Ampere-turns ( q . v .). 

Megohm. A resistance of 1,000,000 ohms. See Ohm. 


Micro. 


A prefix indicating 


1 

1,000,000 ■ 


Microfarad. A capacitance of one-millionth of a 
farad. See Farad. 



GLOSSARY 


271 


Microphone. A loose-contact device, the electric re¬ 
sistance of which varies directly and materially 
with slight differences in mechanical pressure. 

Milli. A prefix indicating - V - of a unit; as a 
“ milliampere. ” 1,UUU 

Motor. A machine that transforms electrical power 
into mechanical power. 

Motor-generator. A transforming device consist¬ 
ing of one or more electrical motors mechanically 
coupled to one or more generators. See Gen¬ 
erator; Motor. 

Oersted. The centimeter-gram-second electromag¬ 
netic unit of magnetic reluctance. See Flux, 
Magnetic. 

Ohm. The international unit of resistance and im¬ 
pedance; substantially equal to 10 9 units of re¬ 
sistance in the centimeter-gram-second system 
of electromagnetic units, and represented by the 
resistance of a column of mercury of specified 
dimensions. 

Oscillating Current. A current resulting from any 
electromagnetic disturbance in a circuit having 
capacity, inductance, and less than the critical 
resistance. If the critical resistance of the cir¬ 
cuit is reached, the current becomes “aperiodic.” 

Oscillations. The surgings in opposite directions 
developed on the discharge of two neighboring con¬ 
ductors. An electric oscillation gives rise to an 
electromagnetic pulse or wave. 

Period. In an alternating current, the time required 
for the current to pass through one cycle of oscil¬ 
lation. See Cycle ; Frequency. 



272 


EVERYDAY ELECTRICITY 


Permeability. The property by which a body per¬ 
mits of magnetic induction; measured by the ratio 
of the amount of such magnetic induction to the 
intensity of the field producing it. See Induction. 

Phantom Circuit. A separate telephone circuit in 
which, without additional wires, each side consists 
of the two conductors of a two-wire circuit in paral¬ 
lel. 

Phase. The fraction of a period of an alternating cur¬ 
rent elapsed from the time when the current passes 
through zero position of reference until it reaches 
a certain relative value. See Alternating Cur¬ 
rent. 

Phot. A unit of illumination consisting of one lumen 
per square centimeter. See Lumen. 

Photometer. A device for the comparison of the in¬ 
tensities of two sources of illumination; as, for ex¬ 
ample, a known with an unknown. 

Polarity. An electrical condition determining the 
direction in which the current tends to flow. 

Polarization. A decrease in the current of a voltaic 
cell, resulting from the formation of a film of hy¬ 
drogen at the positive pole. See Cell, Primary. 

Polarized Relay. A relay that operates in response 
to a change in the direction of the current in the 
controlling circuit. 

Pole. (1) Either terminal of a voltaic cell or battery. 
(The expression terminal is now preferred.) (2) In 
a magnet, that portion in which the attractive 
power centers. 

Polyphase Alternator. A polyphase, synchronous 
alternating-current generator. 


GLOSSARY 


273 


Polyphase Commutating Motor. A motor that re¬ 
ceives its energy from a polyphase alternating- 
current supply system, or from a single-phase 
system, through phase-converting apparatus ex¬ 
ternal to the motor itself. See Motor ; Phase. 

Polyphase Current. Current supplied by an al¬ 
ternator in which separate sets of coils are arranged 
on the armature, giving rise to currents equal in 
frequency and strength but differing in phase. 
See Alternator ; Phase. 

Potential. The power of doing electrical work. See 
Electromotive Force. 

Power. The rate of transfer of energy. In an alter¬ 
nating current, power is the average value of the 
power for the duration of a cycle. The power in 
an electric circuit at any instant is equal to the 
product of the values of the current and voltage at 
that instant, and is generally called the “instan¬ 
taneous power.” See Power, Reactive. 

Power, Reactive. The volt-amperes in alternating 
current; the product of the effective value of the 
voltage across the circuit by the effective value of 
the current. Reactive or apparent power is also 
expressed in kilovolt-amperes (kv.-a.). 

Power Factor. The ratio of the power in the circuit 
to the volt-amperes. In the polyphase circuit, 
the power factor is the ratio of the total ac¬ 
tive power in watts to the total vector voltage 
amperes. See Polyphase Current ; Power, 
Reactive. 

Reactance. In an alternating-current circuit, a prop¬ 
erty resulting from a counter electromotive force 


274 


EVERYDAY ELECTRICITY 


due to inductance or to a back electromotive force 
resulting from capacity or to both. If the circuit 
has inductance, the periodic current lags behind 
the electromotive force. The total reactance is 
equal to the inductive resistance minus the ca- 
pacitative resistance. 

Relay. An electromagnetic device by means of which 
contacts in one circuit are operated by a change in 
conditions in the same circuit or in one or more 
associated circuits, a weak incoming current af¬ 
fecting a strong local current. 

Remanence. The residual magnetism left after the 
magnetizing field has been reduced to zero. 

Repeater. A device for communicating, from one 
circuit to another, electrical impulses, so that they 
will be transmitted without loss of their essential 
characteristics. 

Resistance. Opposition to the passage of a current; 
that property of a conductor whereby the energy 
of the electric current is absorbed and converted 
into heat. 

Resistivity. The resistance between opposite faces 
of a centimeter cube of a given material. 

Resonance. The adjustment of the Capacitance 
(q.v.) and Inductance ( q.v .) in an oscillating 
circuit so that the resulting effective current or 
voltage is a maximum and in harmony as to fre¬ 
quency with an applied alternating electromotive 
force. 

Rheostat. A contrivance with means for readily 
varying resistance in a circuit in which a uniform 
electromotive force is applied. 


GLOSSARY 


275 


Rotary Converter. A machine for transforming al¬ 
ternating current to direct current. The preferred 
term is Synchronous Converter ( q . v .). 

Rotating Field. A magnetic field in which the lines 
of force have a rotary motion. As commonly 
employed, the term especially refers to fields 
produced in fixed coils by polyphase currents. 
See Field ; Polyphase Current. 

Rotor. The rotary portion of an alternator or induc¬ 
tion motor; either the armature, or, in the case of 
the larger units, the revolving field opposed to the 
stator or stationary portion. See Alternator. 

Secondary Battery. See Battery, Storage. 

Self-induction. The property of a circuit that op¬ 
poses by means of a counter electromotive force 
any variation of the current traversing it. 

Short Circuit. A sudden reduction of the resistance 
of a circuit by accident or design, whereby an ab¬ 
normally large current tends to flow between two 
sources of different voltage. 

Single-phase Commutating Motor. A motor that 
receives the whole of its energy from only one 
phase of the alternating-current supply system, 
without requiring external phase-converting ap¬ 
paratus. 

Single-phase Current. A simple periodic alter¬ 
nating current. See Alternating Current. 

Solenoid. A cylindrical coil of wire carrying an elec¬ 
tric current. 

Sounder, Telegraph. An electromagnet arranged 
to give an audible signal when its armature is 
attracted or released. 


276 


EVERYDAY ELECTRICITY 


Spark Gap. In an induction coil or oscillator circuit, 
an interval across which, when the required voltage 
is attained between terminals, a spark passes, 
disrupting the intervening air or other gas. 

Synchronous Converter. A machine for transform¬ 
ing alternating current to direct current. See 
Rotary Converter. 

Synchronous Machine. A machine with a constant 
magnetic field and an armature receiving or de¬ 
livering alternating current in synchronism with 
the motion of the machine. 

Synchronous Motor. A machine structurally iden¬ 
tical with the alternator but operated as a motor. 
See Alternator ; Motor. 

Telephone Repeater. A device for amplifying voice 
current over a one-line circuit to another circuit. 

Terminal. See Pole. 

Three-phase Current. Alternating current in which 
three separate currents, differing one from another 
in phase by one third of a period, are led in a 
common circuit. See Phase. 

Torque. That which tends to change the angular 
velocity of one part of a system with respect to 
another part. 

Transformer. A device for changing the voltage of 
an alternating current and consisting of primary 
and secondary windings. 

Transmission Line. A circuit designed for trans¬ 
mitting relatively large amounts of electric energy. 

Trunk. The wire connection between the switching 
devices and central offices of a telephone system. 

Volt. The international practical unit of electro- 


GLOSSARY 


277 


motive force; the electromotive force that, when 
steadily applied to a conductor whose resistance 
is one ohm, will produce a current of one ampere. 
See Ampere, International ; Electromotive 
Force; Ohm. 

Voltage. Electromotive force, or difference of po¬ 
tential, expressed in volts. See Volt. 

Voltameter. An electrolytic cell for measuring cur¬ 
rent by the amount of chemical action produced. 

Voltmeter. A direct-reading instrument for measur¬ 
ing voltage. 

Watt. The practical unit of power; equivalent to 
the work done at the rate of one joule per second 
or that represented by the flow of a current of one 
ampere at a potential difference of one volt. 

Watt-hour Meter. A device for measuring the 
amount of energy consumed in a circuit. 

Wattmeter. Usually some form of electrodynamom¬ 
eter for measuring electric power, particularly 
in an alternating-current circuit. 

Wave Length. The distance between two waves, from 
crest to crest or from trough to trough. 

Wave Shape. In an alternating current, the shape 
or form of the curve obtained when the instantane¬ 
ous values of the current are plotted against time 
in rectangular coordinates. See Alternating 
Current. 

Waves (or Wave Motion). Periodic disturbances trans¬ 
mitted successively from one portion of a medium. 

Waves, Electromagnetic. A train of electromagnetic 
impulses resulting from electric oscillations. See 
Oscillations. 


278 


EVERYDAY ELECTRICITY 


Weber. A unit of magnetic flux in the practical sys¬ 
tem. 

Work. The product of a force and the distance 
through which it acts. 

X-rays. Short, transverse vibrations in the ether, of 
shorter wave length than light, produced by the 
impact of cathode rays on a solid surface. They 
are capable of penetrating various material sub¬ 
stances and of affecting photographic plates. 
See Cathode Ray. 


BIBLIOGRAPHY 


The student of electricity will find a wide range of popular, 
theoretical, and technical works dealing with electrical 
science, but he must realize that the science of electricity and 
its applications are developing so rapidly that there are com¬ 
paratively few books that are standard as well as strictly 
modern and up-to-date. Accordingly, the technical and 
scientific press perhaps affords the best source of information, 
along with the proceedings of the various scientific and engi¬ 
neering societies. There is also a vast and valuable literature 
that has been developed by the various manufacturing com¬ 
panies in the form of bulletins and other printed matter; 
and although this is often frankly commercial, yet it is well 
presented and available to the general reader. 

There are, however, a number of books, such as those 
listed below, that can be suggested for reading; and although 
these are of varied merit, attempt has been made to mention 
those that are generally accessible, that represent recent 
practice, and that will supply technical and advanced infor¬ 
mation not possible in a volume of the nature and scope of 
the present one. 

GENERAL PHYSICS 

The chapters on electricity and magnetism in the modern 
treatises on physics are well prepared, and in recent texts 
discuss modern theory and practice. A few volumes of 
this kind are: 

Comstock, D. F., and Troland, L. T. The Nature of 
Matter and Electricity. New York: D. Van Nostrand 
Company. 1917. Revised edition, 1921. 


280 


EVERYDAY ELECTRICITY 


A readable and nontechnical discussion of modern theories, 
including those regarding the atom and the electron. 

Ferry, E. S. General Physics. New York: John 
Wiley and Sons, Inc. 1921. 

A college textbook that has excellent chapters on electric¬ 
ity and magnetism. 

Franklin, W. S., and MacNutt, B. General Physics. 
New York : McGraw-Hill Book Company. 1919. 

A textbook for colleges and technical schools, with a full 
discussion of electrical principles. 

Millikan, R. A. The Electron. Chicago: The Uni¬ 
versity of Chicago Press. 1917. 

An excellent comprehensive summary of electrical theory 
as it had been developed up to the time of the book’s publi¬ 
cation. 

Mills, J. Within the Atom. New York: D. Van 
Nostrand Company. 1921. 

A popular view of electrons and quanta, designed to give 
nontechnical readers a familiarity with the basis of physical 
science. 

Webster, D. L., Farwell, H. W., and Drew, E. R. Gen¬ 
eral Physics for Colleges. New York: The Century 
Company. 1923. 

Discusses modern theories of electricity and magnetism, 
especially in relation to ideas of matter, space, time, and 
gravitation. 

HISTORICAL 

Fleming, J. A. Fifty Years of Electricity. London 
and New York : The Wireless Press. 1921. 

An interesting summary of the development of the use of 
electricity, and its more important applications. It is the 
work of a British engineer and consequently refers more to 
European practice. It deals with only the half-century re¬ 
ferred to in the title, but within that time the more important 
developments are, of course, included. 


BIBLIOGRAPHY 


281 


ELEMENTARY AND GENERAL 

Chief Signal Officer’s Office. Elementary Elec¬ 
tricity. (Training Pamphlet Number 1.) Washington. 
1921. 

A simple treatise issued by the War Department for the 
training of men who know nothing of electricity. 

Timbie, W. H. Elements of Electricity. New York: 
John Wiley and Sons, Inc. 1910. 

Timbie, W. H. Essentials of Electricity. New York: 
John Wiley and Sons, Inc. 1912. 

HANDBOOKS 

In electrical engineering, valuable material has been assem¬ 
bled in the form of handbooks. These are both complete and 
reliable, and in many cases have references to the standard 
and current literature of the subject. In this field, the follow¬ 
ing volumes can be specially recommended : 

Fowle, F. F., Editor-in-chief. Standard Handbook for 
Electrical Engineers. New York: McGraw-Hill Book 
Company. Fourth edition, 1915. 

A complete and convenient summary that takes up the 
subject by sections, each of which is devoted to a special 
topic, with subdivisions. 

Pender, H., Editor-in-Chief. Handbook for Elec¬ 
trical Engineers. New York: John Wiley and Sons, 
Inc. Revised edition, 1922. 

A comprehensive manual of current practice in electrical 
engineering. 


ELECTRICAL ENGINEERING 

Useful textbooks in this field have been prepared by teach¬ 
ers of electrical engineering. The following volumes, dealing 
with both theory and practice, are of recognized value: 


282 


EVERYDAY ELECTRICITY 


Franklin, W. S. Elements of Electrical Engineer¬ 
ing. Volume I, Direct and Alternating Currents and Sys¬ 
tems, 1917. Volume II, Electric Lighting and Miscellaneous 
Applications of Electricity, 1919. New York: The Mac¬ 
millan Company. 

Morecroft, J. H., and Hehre, F. W. Continuous Cur¬ 
rent Circuits and Machinery. New York: John Wiley 
and Sons, Inc. 1923. 

A useful elementary textbook. 

Steinmetz, C. P. Theoretical Elements of Electrical 
Engineering. New York: McGraw-Hill Book Company. 
Fourth edition, 1915. 

A general introduction to advanced mathematical con¬ 
siderations. 

Timbie, W. H., and Bush, V. Principles of Electrical 
Engineering. New York: John Wiley and Sons, Inc. 1923. 

A college first course in Electrical Engineering. 

DIRECT CURRENT 

Langsdorf, A. S. Principles of Direct Current Ma¬ 
chines. New York: McGraw-Hill Book Company. Revised 
edition, 1919. 

A standard treatise. 

Pender, H. Direct-current Machinery. New York: 
John Wiley and Sons, Inc. 1922. 

Timbie, W. H. Essentials of Electricity : A Text¬ 
book for Workmen and the Electrical Trades. New 
York: John Wiley and Sons, Inc. 1915. 

ALTERNATING CURRENTS 

Lawrence, R. R. Principles of Alternating Cur¬ 
rents. New York : McGraw-Hill Book Company. 1922. 

Timbie, W. H., and Higbie, H. H. Alternating Cur¬ 
rent Electricity. New York: John Wiley and Sons, Inc. 
First Course, 1915. Second Course, 1916. 


BIBLIOGRAPHY 


283 


The First Course is an elementary introduction to alter¬ 
nating-current machinery and phenomena. The Second 
Course explains in greater detail the construction and char¬ 
acteristics of alternating-current apparatus. 

Timbie, W. H., and Higbie, H. H. Essentials of Al¬ 
ternating Currents. New York: John Wiley and Sons, 
Inc. 1919. 

PRIMARY BATTERIES 

Bureau of Standards. Electrical Characteristics 
and Testing of Dry Cells. (Circular Number 79.) Wash¬ 
ington. 1919. 

Carhart, H. S. Thermo-electromotive Force in 
Electric Cells, the Thermo-electromotive Force be¬ 
tween a Metal and a Solution of One of Its Salts. 
New York : D. Van Nostrand Company. 1920. 

Cooper, W. R. Primary Batteries : Their Theory, 
Construction and Use. London: Benn Brothers, Ltd. 
New and revised edition, 1920. 

ELECTRIC LIGHTING 

Bureau of Standards. Materials for the Household 
(Circular Number 70.) Washington. 1917. 

Discusses electric lamps. 

Ferguson, O. J. Electric Lighting. New York: Mc¬ 
Graw-Hill Book Company. 1920. 

Luckiesh, M. Lighting the Home. New York: The 
Century Company. 1920. 

WIRING 

The convenience and safety of a modern installation de¬ 
pend in large measure upon the wiring and the arrangement 
of the conductors. It is most important to have the work 
done in accordance with the regulations of the fire-insurance 
authorities, whose code is made a basis of such volumes as: 


284 


EVERYDAY ELECTRICITY 


Cook, A. L. Interior Wiring. New York : John Wiley 
and Sons, Inc. 1917. 

A practical treatise on wiring for both light and power 
service. 

National Board of Fire Underwriters. National 
Electric Code. Chicago. 

ELECTRIC TRANSPORTATION 

The electric railway for both urban and trunk-line service 
has been best discussed in the proceedings of the technical 
engineering societies. A few significant volumes have, how¬ 
ever, been written in this field — such as : 

Carter, F. W. Railway Electric Traction. New 
York : Longmans, Green and Company. 1922. 

A technical discussion of the electrification of steam rail¬ 
ways in the United States and Europe. 

Manson, A. J. Railroad Electrification and the 
Electric Locomotive. New York: Simmons-Boardman 
Publishing Company. 1923. 

A practical work dealing with important American sys¬ 
tems of installation and operation. 

ELECTRIC WAVES AND RADIO COMMUNICATION 

Ballard, W. C. Elements of Radio Telephony. 
New York : McGraw-Hill Book Company. 1922. 

Fleming, J. A. The Principles of Electric Wave 
Telegraphy and Telephony. London: Longmans, Green 
and Company. 1916. 

Hogan, J. V. L. The Outline of Radio. Boston: 
Little, Brown, and Company. 1923. (The Useful Knowl¬ 
edge Books.) 

A volume giving a clear and direct explanation of the prin¬ 
ciples and ordinary applications of radio communication. 


BIBLIOGRAPHY 


285 


Lauer, H., and Brown, H. L. Radio Engineering 
Principles. New York: McGraw-Hill Book Company. 
1919. 

Morecroft, J. H. Principles of Radio Communica¬ 
tion. New York: John Wiley and Sons, Inc. 1921. 

Pierce, G. W. Electric Oscillations and Electric 
Waves with Application to Radio Telegraphy and 
Incidental Application to Telephony and Optics. New 
York : McGraw-Hill Book Company. 1920. 






INDEX 


Accumulator. See Battery, 
storage. 

Albany Academy, scene of 
Henry’s experiments, 101 
Alternating current, early use 
of, 19; generation and 
transmission of, 96-97 
Alternating-current motor, 
advantages and disadvan¬ 
tages of, 92-93 ; three main 
groups of, 93 ; types of, for 
electric traction, 203 
Alternator, 85, 89, 90-91; 
collector rings of, 88; re¬ 
volving-field type of, 90 
Aluminum, produced in elec¬ 
tric furnace, 230 
Aluminum conductors, 191 
Amber, properties of, known 
to ancients, 6 

American Morse code, signals 
of, 108-109 

Ammeter, explained, 51-53 
Ampere, defined, 48-49 
Amplifiers for telephone cir¬ 
cuits, 148 

Anode of primary cell, 38; of 
X-ray tube, 241 
Anticathode rays. See X- 
rays. 

Arc, 155, 218; flame, 157; 
luminous, 158; mercury, 
160 


Arc furnace, 227 
Arc lamp, inclosed, 157 
Arc lamp, open, 156; in 
lighthouse at South Fore¬ 
land, 17 

Arc lamps, uses of, 158 
Arc lighting, with alternat¬ 
ing current, 97 

Armature, of dynamo, 78; 
ring, 17; shuttle-wound, 
17 

Atlantic Ocean, cables cross¬ 
ing, 124 

Atoms, early ideas about, 
9-10 

Bar Magnet, properties and 
phenomena of, 30-33 
Battery, storage, 70; appli¬ 
cation of, 75; Edison’s al¬ 
kaline type of, 74 ; “ iron¬ 
clad”, 72-73; lead, 70; 
on submarines, 211 
Battery, voltaic, described, 
36-37 

Bell, A. G., invents the tele¬ 
phone, 18; original tele¬ 
phone circuit of, 127 
Brass plating, 222 
Bremer, H., devises flame arc, 
157 

Bridge duplex telegraph sys¬ 
tem, 113 


287 



288 


INDEX 


Brush, C. F., pioneer in 
American arc lighting, 18, 
155-156 

“Bug.” See Vibroplex. 

Bulb, X-ray, 241, 244-245 
“Busy” signal, by telephone 
operator, 135-136 

Cable, Submarine, auto¬ 
matic transmission by, 121; 
first laid between America 
and Great Britain, 16; 
structure of, 118 
Cable, submarine, artificial, 
122 

Cable, underground, between 
Boston and Washington, 150 
Cable relays, 122 
Cable ships, 123 
Cables, telephone, develop¬ 
ment of, 145-146 
Calcium carbide, an electro¬ 
chemical product, 230-231 
Candle, electric, invented by 
Jablochkov, 155 
Candle power, defined, 162 
Carbon filament for electric 
lamps, 160, 161 
Carborundum (silicon car¬ 
bide), a product of the 
electric furnace, 231 
Carlisle, Sir A., decomposes 
water, 14 

Carrier multiplex telephony 
and telegraphy, essential 
method of, 152 

Carty, J. J., experiments with 
return telephone wire, 144 
Cathode, of primary cell, ex¬ 


plained, 38; of X-ray tube, 
defined, 241 

Cell, Bunsen, 160 ; Clark, 57; 
closed-circuit, 42; Daniell, 
42-43; dry, 45-47; grav¬ 
ity, 42-44; Leclanche, 42, 
44-45; open-circuit, 42; 
storage, 70; voltaic, 14, 
36-37; Weston, 57 note 
Chemical action, forces out 
electrons at negative pole 
of battery, 12; in primary 
cell, 38-39 ; maintains dif¬ 
ference of potential in vol¬ 
taic cell, 36 

Chemicals manufactured elec- 
trolytically, 226 
Chicago, Milwaukee and St. 
Paul Railway, electric trac¬ 
tion on,208 

Circuit, magnetic, no insula¬ 
tion for, 35 

Circuit breaker, function of, 
174; magnetic blow-out 
type of, on railways, 204 
Clarke, E. M., devises mag¬ 
neto-machine, 17 
Clouds, electrical charge of, 
250-251 

Common-battery telephone 
system, explained, 138; in¬ 
troduction of, 132-133 
Commutator, explained, 79- 
81; used in crude form by 
Pixii, 16 

Compass, magnetic, simple 
forms of, 31-32 
Compass needle, movement 
of, when near conductor, 14 



INDEX 


289 


Condenser, explained, 27-29 
Conductivity, relative, ex¬ 
amples of, 55 

Conductor, explained, 12, 55- 
56; types of, for trans¬ 
mission lines, 191 
Conduit electric railways, de¬ 
veloped, 198 

Conduits for wiring in build¬ 
ings, 171 

Continental (International) 
Morse code, 111; signals 
of, 108-109 

“Contour system” of light¬ 
ning conductors, used in 
Europe, 257 

Coolidge X-ray tube, de¬ 
scribed, 245-246 
Copper plating, 220-221 
Copper refining, electrolytic, 
224-225 

Crookes, Sir W., studies pass¬ 
age of electricity through 
gases, 20 

Crookes tube, explained, 241 
“Crown of cups” of Volta, 
explained, 37 

Current, electric, effects of, 
13; induced, 62-64 ; meas¬ 
urement of, 48-49; scien¬ 
tific explanation of, 12 
Cycle, explained, 86 

Daniell Cell, described, 
42-43; type of, used with 
telegraph, 105 

D’Arsonval galvanometer, ar¬ 
rangement of, 51 
Dash of Morse code, 104, 110 


Davenport, T., devises early 
motor-driven car, 18 
Davy, Sir H., develops elec¬ 
tric arc, 155; experiments 
and discoveries of, with 
voltaic current, 14; pio¬ 
neer in electrochemistry, 
218, 226 ; remark of, about 
voltaic battery, 37 
“Dead-man’s handle”, safety 
device, 202 

Decomposition, electrolytic, 
in electroplating, 220; of 
salts, 14, 219; of water and 
salt solutions, 14 
De Forest, L. See Forest, L. 
de. 

“De Magnete”, Gilbert’s, in¬ 
troduces term “electricity ”, 
6 

Diagnosis with X-rays, 248 
Dial device in telephony, de¬ 
scription of, 140 
Differential relay in duplex 
telegraphy, 112-113 
Direct current, 96 et seq. 
Direct-current generator, 
structure and action of, 
79-82 

Direct-current motor, prin¬ 
ciple and action of, 82-83, 
79-82 

Dot, of Morse code, 104, 110 
Drive, electric, for battle¬ 
ships, 211 

Dry cell, description of, 45-47 
Duplex telegraphy, principle of 
operation of, 112-113; with 
submarine cable, 121-122 



290 


INDEX 


Dynamo, compound-wound, 
81; principle of, 76-78; 
series-wound, 81; shunt- 
wound, 81 

Edison, T. A., alkaline stor¬ 
age battery of, 74; first 
railway experiments of, 19, 
193; invents incandescent 
light, 18, 160, 168 
Electric — drive, 178; ele¬ 
vators, 180-183; furnace, 
218, 227; heating, 213; 
lighting, 154; locomotives, 
204-206 ; motor, 176, 178- 
179; power, 179; railways, 
18, 193-194 

Electrical — machines, 26; 
measurements, 48; units, 
48 

Electricity, applications of, 
16; at rest, 22; early as¬ 
pects of, 6; first so called 
by Gilbert of Colchester, 
7; fundamental nature of, 
3; history of, 6; impor¬ 
tant discoveries in, 13; 
nature of, 8; on shipboard, 
210; on the farm, 184-186 
Electricity, negative, 7, 11 
Electricity, positive, 7 
Electrification of railways, ad¬ 
vantages of, 208 
Electrochemistry, importance 
of, 218 

Electrolyte, action of, 41 
Electromagnet, how prepared, 
34 ; invention of, by Stur¬ 
geon, 15 


Electromagnetic — telegraph, 
104; theory of light, 19; 
waves, 236-238 
Electromotive force, of cells 
in series and in parallel 
(multiple), 39 

Electron, nature of, 9-11; 
surrounded by magnetic 
field, 33 

Electrons in voltaic battery, 
36; motion of, in cell, 38- 
39; number of, 48; pass¬ 
age of, 25 

Electrophorus, explained, 25 
Electroplating, fundamentals 
of, 219 

Electroscope, gold-leaf, 24-25 
Electrotyping, process of, 
222-223 

Elevators, electric, automatic, 
183; description of, ISO- 
183 ; motors for, 181-182 
Energy, electrical, applica¬ 
tions of, 176 

Faraday, M., discovers pro¬ 
duction of induced current 
in conductor moved across 
magnetic field, 15-16; work 
of, utilized by Maxwell, 234 
Fay, C. du, discovers pro¬ 
duction of electricity with 
cat’s fur, 7 
Field, magnetic, 14 
Field, S. D., experiments of, 
in electric traction, 193 
Field coils, of alternator, 90; 

of dynamo, 79 
Field of force, magnetic, 33 



INDEX 


291 


Filaments for incandescent 
lamps, 162 

Fire-alarm telegraph, opera¬ 
tion of, 124 

Fire Underwriters, National 
Board of, wiring table of, 
172 

“Fireless cooker”, electric, 
216-217 

Fizeau, A., measures velocity 
of light, 234 

Fluorescence of vacuum tube, 
241-242 

Fluorescent screen, 243 

Forest, L. de, patents grid 
audion, 148 

Foucault, J. B. L., uses gas 
carbon for electrodes, 155 

Foucault currents in arma¬ 
ture, 90 

Franklin, B., considers light¬ 
ning and electricity iden¬ 
tical, 250, 252-253; intro¬ 
duces terms “positive” and 
“negative”, 7; studies elec¬ 
trical phenomena, 7, 8, 22 

Franklin pane, 28 

Frequency, defined, 86; stand¬ 
ardized, 91 

Furnace, electric, arc type of, 
227; induction type of, 
228; resistance type of, 228 

Fuse, purpose and arrange¬ 
ment of, 172-173 

Galvanometer, action of, 49- 
51 

Galvanometer, mirror, in¬ 
vented by Lord Kelvin, 119 


Generator, development of, 
16; direct-current, 79 
Gilbert, W., of Colchester, ex¬ 
periments with static elec¬ 
tricity, 6, 22; originates 
term “electricity”, 7 
Glass rod, charged by friction 
with silk, 22 
Gold plating, 220, 222 
Gramme, Z. T., invents ring 
armature, 17 

Gramme dynamo, used for 
arc lamps, 155 

Graphite, artificial, from elec¬ 
tric furnace, 232 
Gravity cell, described, 43-44; 

used with telegraph key, 105 
Great Northern Railroad, 
electric traction on, 208 
Greeks, ideas of, regarding 
electricity, 6, 9, 22 
Grove cell, used for arc light¬ 
ing, 155, 160 

Halske, J. G., builds experi¬ 
mental railway, 19 
Heater, electric, based on 
resistance, 213; for room, 
215; monoplane, 214; 
open-coil, 214 

Heating appliances, energy 
demands of, 217 
Heating units, materials of, 214 
Henry, J., discovers oscilla¬ 
tory discharge of Leyden 
jar, 234; makes improve¬ 
ments in electromagnet, 
101; principle in relay dis¬ 
covered by,107 



292 


INDEX 


Heroult furnace, 229 
Hertz, H., researches of, re¬ 
garding electromagnetic 
waves, 19, 234-238 
Hertz oscillator, 235-236 
Hewitt, P. C., invents mer¬ 
cury arc, 159 

Hogan, J. V. L., author of 
“The Outline of Radio”, 
240 

Holtz machines, 27 
Horsepower, defined, 60 
“Hot plate” of electric range, 
216 

Hydroelectric plants, 189-190 

Illinois Central Rail¬ 
road, electrification of, 206 
Incandescent lamps, early ex¬ 
periments with, 160; effi¬ 
ciency of, 174; gas-filled, 
161, 166; “Gem”, 162, 
163-164; made practicable 
by dynamo, 160 
Induced currents, 62-64 
Inductance, 68-69 
Induction, 67; discovery of, 
15; magnetic, 32 
Induction coil, 65-67; 

“break” mechanism of, 66 
Induction furnace, 228 
Induction motors, 93 
Inductor-alternator, applica¬ 
tion of, 91 

Industrial plants, electricity 
in, 177 

Industry, electricity in, 177- 
180 

Influence machines, 27 


Insulators for power lines, 
arrangement of, 191 
Internal resistance, 39, 41, 42 
International Morse code, sig¬ 
nals of, 108-109 
Ions, 41 

“Ironclad” battery, structure 
of, 72-73 

Isolated lighting systems, 
169-170 

Jablochkov, P., invents elec¬ 
tric candle, 155 
Jack of telephone switch¬ 
board, 135 

Jandus improved arc lamp, 
157 

Joule, J. P., makes researches 
in electric heating, 213 

Kelvin, Lord, invents mirror 
galvanometer, 119; in¬ 
vents siphon recorder, 119- 
120; studies electric oscil¬ 
lations, 234 

Key, telegraph, 104-106 
Kilowatt, defined, 60 

Lead Battery, action of, 70- 
71 

Leclanche, G., devises Le¬ 
clanche cell, 44 
Leclanche cell, 42, 44-45 
Leucippus, atomic theory of, 9 
Leyden jar, Henry investi¬ 
gates discharge of, 234 ; in¬ 
vented, 27 

Light, velocity of, 233, 234, 
236; waves of, 233 




INDEX 


293 


Lighting, electric, central sta¬ 
tions for, 161; early at¬ 
tempts in, 154-155 
Lighting systems, isolated, 

170 

Lightning, how caused, 250; 

protection against, 252-256 
Lines, telephone, early experi¬ 
ence with, 143-144 
Lines of force, magnetic, 33, 
35 

Loading coils, introduction 
and nature of, 146-148 
Local circuit, of telegraph, 
107 

Locomotives, electric, intro¬ 
duced on American rail¬ 
ways, 95, 203-206 
Lodge, Sir O., studies elec¬ 
tromagnetic waves, 19 
Long-distance telephony, 
operation of, 149-152 
Lorentz, H., investigates na¬ 
ture of electricity, 9 
Lucretius, acquainted with 
magnetism, 30; atomic 
theory of, 9 
Lumen, defined, 162 
Luminosity decreases with de¬ 
cline of voltage, 97 

Machine-switching System, 
telephone, 139 

Magnesia, gives name to mag¬ 
net, 30 

Magnet, action of, as studied 
with iron filings, 31-33; 
artificial, 30 ; bar, 30 ; gen¬ 
eral discussion of, 30-34 


Magnetic — blow-out, 204; 
circuit, 35; engine, in¬ 
vented by Henry, 101; 
field, 14; field of force, 33; 
lines of force, 33, 35; poles, 
30; properties of steel, 31 
Magnetism. See Magnet. 
Magneto, invention and im¬ 
provement of, 16-17; mod¬ 
ern construction of, 76-78; 
used on telephone circuit, 
130-131 

Magneto-machine. See Mag¬ 
neto. 

Marconi, G., work of, in 
electric-wave telegraphy, 
19, 239-240 

Marks, L. B., invents inclosed 
arc lamp, 157 
Matter, theories of, 10 
Maxwell, J. C., formulates 
electromagnetic theory of 
light, 19; studies electro¬ 
magnetic waves, 234, 236 
“Mazda” lamps, 162 
Measurements, electrical, dis¬ 
cussion of, 48-61 
Menlo Park, scene of Edison’s 
early experiments, 19 
Mercury arc, nature of, 159- 
160 

Metallic circuits for telephone, 
144 

Microphone, 129 
Milliammeter, 55 
Millivoltmeter, 55 
Mirror galvanometer, in¬ 
vented by Lord Kelvin, 119 
Molecules, 9-10 



294 


INDEX 


Monoplane heater, 214 
Morse, S. F. B., invents tele¬ 
graph, 16, 104 

Morse telegraph code, de¬ 
vised by Morse, 105; ex¬ 
plained, 110; signals of, 
108-109 

Motor, advantages of, 176, 
178-179; alternating-cur¬ 
rent, 93; bi-polar arrange¬ 
ment of, 84; compound- 
wound, 84; direct-current, 
82; induction, 93; poly¬ 
phase, 93; railway, 195- 
196; regulation of, 84-85; 
series-wound, 84; shunt- 
wound, 84; single-phase 
series, 95; “squirrel-cage”, 
93-94; synchronous, 95; 
wound-rotor, 94 
Motor generators, 98 
Muirhead and Taylor, duplex 
system of cable transmis¬ 
sion devised by, 122 
Multiple arrangement of cells, 
40 

Multiple switchboard for tele¬ 
phone, 134 

Multiple-unit control for rail¬ 
way motors, 202 
Multiplex telegraph, descrip¬ 
tion of, 114-117 

Negative Charge, nature 
of, 11 

“Negative” electricity, first 
so called by Franklin, 7 
New Mexico , first battleship 
to be electrically driven, 211 


New York Central Railroad 
electrification, 200, 205 
New York, New Haven and 
Hartford Railroad electri¬ 
fication, 95 

New York subways, third-rail 
construction in, 200 
News-bulletin service, print¬ 
ing telegraph used for, 117 
Nicholson, W., decomposes 
water, 14 

Nickel plating, by electroly¬ 
sis, 220-221 

Nickel refining, by electroly¬ 
sis, 225 

Nickel steel, used for resis¬ 
tance wires, 214 
Nonconductor, defined, 12 

Ocean Cable, modern con¬ 
struction of, 118 
Oersted, H. C., discovers 
magnetic field of conduc¬ 
tor, 14 

Ohm, defined, 56 
Ohm’s law, discussion of, 58- 
59 

Open-coil heater, 214 
Oscillator of Hertz, 235-236 

Pacinotti, A., invents ring 
armature, 17 

Parallel arrangement of cells, 
40 

Party lines of telephone, 133 
Pennsylvania Terminal, New 
York, electrification in, 205 
Period, defined, 86 
Permeability, defined, 35 



INDEX 


295 


Phantom circuit in telephony, 
151 

“Pickling” in electroplating, 
221 

Pith balls, experiments with, 
22-23 

Pixii, H., invents magneto¬ 
machine, 16 

Plante type of storage cell, 
71-72 

Plug of telephone switch¬ 
board, 136 

Polarization of cell, 41-42, 43 
Polarized relay in duplex teleg¬ 
raphy, 113 

Pole-changing key for cable 
transmission, 121 
Poles for transmission lines, 
191 

Polyphase induction motor, 93 
“Positive” electricity, first so 
called by Franklin, 7 
Potential, difference of, in 
battery cells, 39-40 
Power, electric, 179 
Primary cell, described, 37-38 
Primary winding of induction 
coil, 66 

Printing telegraph, explained, 
117 

Protons, 10-11 

Pupin, M. I., devises loading 
coils for telephone circuits, 
146 

Quadruplex Telegraph, 
113-114 

Quadr up lex-duplex telegraph, 

116 


Radiotelegraphy, 239-240 
Radiotelephone, 240 
Radium employed with gold- 
leaf electroscope, 24 
Railway, electric, beginnings 
of, in America, 18, 193- 
194; current supply for, 
196-197; drop of voltage 
in, 98 

Railway motors, alternating 
current for, 203; control¬ 
ling systems for, 201-202; 
early types of, 195-196 
Ranges, electric, 216 
Receiver, telephone, 128 
Recorder, siphon. See Si¬ 
phon recorder. 

Recorder, telegraph, included 
in Morse’s original appara¬ 
tus, 104 

Refining of metal, by elec¬ 
trolysis, 224-226 
Regenerative braking, 209 
“Relativity”, 20 
Relay, differential type of, 
113 ; polarized type of, 113 ; 
telegraph, 106-107 
Repeater, telegraph, 107, 112; 
telephone, 150 

Repeating amplifiers, tele¬ 
phone, experiments with, 
148 

Repulsion of like magnetic 

poles, 32 

Resistance, explained, 55 
Resistance, internal, 39, 41-42 
Resistance furnace, 228 
Resistance wires in heating 
apparatus, 214 



296 


INDEX 


Revolving-field alternator, ex¬ 
plained, 90 

Ring armature invented by 
Pacinotti and Gramme, 17 
Roentgen, W. K., discovers 
nature and effects of X-rays, 
20, 242-243 
Roentgen rays, 241 
Rotary converter. See Syn¬ 
chronous converter. 

Salts, decomposition of, 219 
Saxton, J., devises magneto¬ 
machine, 17 

Sealing wax electrified when 
rubbed with cat’s fur, 7, 11 
Searchlight, arc lamps used 
for, 158 

Secondary cell. See Storage 
cell. 

Secondary winding of induc¬ 
tion coil, current in, 67 
Self-induction. See Induc¬ 
tance. 

Series arrangement of battery 
cells, 39 

Series multiple switchboard 
for telephone, 134 
Side circuit, in long-distance 
telephony, 151-152 
Siemens, W. von, builds ex¬ 
perimental railway line, 19; 
experiments with electric 
traction, 193; invents shut¬ 
tle-wound armature, 17 
Silver plating, 220 
Single-phase current, ex¬ 
plained, 87-89; in trans¬ 
mission, 190; on New 


York, New Haven and Hart¬ 
ford, 205 

Single-phase series motors, 
used in railway work, 95 
Single reduction gear motors, 
developed at Westing- 
house works, 196 
Sodium, Davy isolates, as 
element, 14 
Solenoid, 62 

Sounder, telegraph, structure 
and action of, 105 
Sprague, F. J., installs first 
commercial electric railway, 
19 

Spring jack of telephone 
switchboard, 134 
“Squirrel cage” motor, con¬ 
struction of, 94 
Standard cell (Weston), 57 
note 

Standard resistance, defined, 
56 

Static electricity, 22-29 
Steel, electric furnaces for, 

229 

Steradian, defined, 162 
Stock ticker, printing tele¬ 
graph used for, 117 
Storage battery, alkaline, of 
Edison, 74 

Storage battery, “ironclad”, 
72-73 

Storage batteries, application 
of, 75; on submarines, 211 
Storage cell, action of, 70; 

Faure type of, 71-72 
Siphon recorder, invented by 
Lord Kelvin, 119-120 



INDEX 


297 


Sturgeon, W., invents elec¬ 
tromagnet, 15 

Submarine, electrical appara¬ 
tus in, 211 

Submarine telegraphy, devel¬ 
opment of, 118-119 
Submersible, electrical appar¬ 
atus in, 211 

Sulphion, electronegative ion, 

41 

Switchboard, telephone, de¬ 
velopment and improve¬ 
ment of, 131-137; opera¬ 
tions at, 137 

Switchboard, telephone toll, 
139 

Synchronous alternator, 91 
Synchronous converter, 98- 
100 

Synchronous motor, 19, 95 

Tantalum Incandescent 
Lamps, 162, 164-165 
Telegraph, automatic device 
for, 114; current supply 
for, 111; duplex, 112-113; 
fire-alarm, 124; invented 
by Morse, 16; multiplex, 
114-115; principle of, 104 ; 
printing, 117; quadruplex, 
113; quadruplex-duplex, 
116; submarine, 118; 

Wheatstone automatic, 114 
Telegraph key, 104-106 
Telegraph recorder, 104 
Telegraph relay, 106-107 
Telegraph repeater, 107- 

112 

Telegraph sounder, 105 


Telephone, common-battery 
system of, 132; dial instru¬ 
ment of, 140; fundamentals 
of, 126 ; long-distance, 150 ; 
long-distance circuits of, 
147; machine-switching 
system of, 139; magneto 
for, 131; party lines of, 

133 ; receiver of, 128; series 
multiple switchboard of, 

134 ; transcontinental, 151; 
underground cable for, 150 

Telephone cables, 145 
Telephone hook switch, 131 
Telephone lines, 143-144; 

transcontinental, 151-152 
Telephone repeaters, on Bos- 
ton-Washington line, 150 
Telephone “selector frame” 
of machine-switching sta¬ 
tion, 141 

Telephone switchboard, 131- 
136; for toll lines, 139; 
operations at, 137 
Telephone transmitter, 129 
Tesla, N., invents induction 
motor, 93 

Thales of Miletus, observes 
electrification of amber, 6 
Theophrastus, records elec¬ 
trification of amber, 6 
Third-rail transportation sys¬ 
tems, 199-200 

Thomson, J. J., discovers 
electron, 20; studies deflec¬ 
tion of cathode rays by 
magnet, 242 

Thomson, Sir W. See Kelvin, 
Lord. 



298 


INDEX 


Three-phase current, ex¬ 
plained, 88-89; in trans¬ 
mission, 190 

Three-wire system of current 
distribution, 168 
Thunder, explained, 252 
Tin scrap, refining of, by 
electrolysis, 226 
Toepler machines, 27 
Toll switchboard, telephone, 
139 

Transfer switchboard for tele¬ 
phone central stations, 134 
Transformer, care of, 31; ex¬ 
plained, 67-68, 98-99; in 
alternating-current trans¬ 
mission, 188; invention of 
19 

Transmission lines, 187; long¬ 
distance, 188 

Transmitter, telephone, 129 
“Trimming” of arc lamps, 
156-157 

Trolley line, first, 194 
Trunk lines between switch¬ 
boards, 134 

Tube, focus, for X-rays, 243- 
245 

Tungsten lamps, 162,165-166 
Turboalternator, 100 
Turbogenerator, described, 
92; on shipboard, 211 
Two-fluid theory of electric¬ 
ity, 8 

Two-phase current, explained, 
88; in transmission, 190 


Underground conduit rail¬ 
ways, 198 

Units, electrical, 48 et seq. 

Vacuum Tube, for X-rays, 
241 

Vacuum-tube detectors, 240 
Vacuum-tube repeater, 149 
Van Depoele, C. J., builds 
first overhead electric line, 
193 

Vibroplex, telegraph key, 106 
Volt, explained, 57 
Volta, A., discovers voltaic 
cell, 14, 36-37 

Voltaic cell, current developed 
by, 36-37; discovered by 
Volta, 14 

Voltmeter, described, 53-54 
Vulcanite, charged by fric¬ 
tion with fur, 23 

Water, decomposition of, 
14 

Watt-hour meter, described, 
59-61 

Wattmeter, 60 
Wave detectors, 237-238 
Waves, electric, 233; electro¬ 
magnetic, 236-237; light, 
233; sound,233 
Weber, W., establishes theory 
of electromagnetism, 8-9 
Western Union Telegraph 
Company, use of multiplex 
system by, 115 
Weston normal cell, 57 note 
Wheatstone automatic tele¬ 
graph, 114 


Underground Cable, for 
telephone, 150 



INDEX 


299 


Wimshurst machine, 27 
Wiring, household, sugges¬ 
tions for, 171 

Wound-rotor motor, de¬ 
scribed, 94-95 

X-Rays, absorption of, 243; 
diagnosis with, 248; dis¬ 


covery of, 20; in medicine 
and surgery, 246-249 ; pho¬ 
tographs by, 243, 247; 

therapeutic effect of, 248; 
transparency of bodies to, 
243; tubes for, 244-245 

Zinc Plating, 220, 222 





























